document_title: Global wind patterns

question_text: what global prevailing winds move from the east to the west along the equator

text: Global wind patterns

text:
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text: It has been suggested that this article be merged into Prevailing winds. (Discuss) Proposed since June 2017.

text: This article does not cite any sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (September 2013) (Learn how and when to remove this template message)

text: This article is in a list format that may be better presented using prose. You can help by converting this article to prose, if appropriate. Editing help is available. (November 2017)

text: Global wind patterns: Winds are named by the direction from which they blow. The globe is encircled by six major wind belts, three in each hemisphere. From pole to equator, they are the polar easterlies, the westerlies, and the trade winds. All six belts move north in the northern summer and south in the northern winter. Each belt occupies about 30 degrees of latitude, that is, one third of the way from the pole to the equator.

text: Polar Easterlies: At about the latitude of Norway, Alaska U.S.A, and northward (60-90 degrees), the Polar easterlies blow irregularly from the east and north.

text: Polar Front: Between the polar easterlies and the westerlies is the polar front.

text: Prevailing Westerlies: At about the latitude of Western Europe and Continental U.S. (30-60 degrees), the Westerlies blow from the west, tending somewhat toward the north. This causes most weather in the United States to move from west to east.

text: Horse Latitudes: Where the Westerlies meet the trade winds at about 30 degrees (Jacksonville, Florida) is the Horse latitudes, also Variables of Cancer, Subtropical High, or Subtropical ridge. This is a region of high pressure, dry air, and variable winds, and is associated with deserts over land.

text: Trade Winds: South of about 30 degrees the northern or northeast trade winds blow mostly from the northeast toward the equator. These were the sailor's favorite winds, since the weather was warm, and the winds usually blew steadily in an advantageous direction. Columbus used these to sail to the Caribbean.

text: Doldrums: At about the equator is Intertropical Convergence Zone or doldrums, a region of light and irregular wind broken by occasional thunderstorms and squalls. The width and exact location of the doldrums were hard to predict. Sailing ships are sometimes becalmed here for many days waiting for a proper wind.

text: Southern hemisphere: In the southern hemisphere the belts are reversed. The southeast trade winds blow from the southeast toward the equator. The southern equivalent of the horse latitudes (or Variables of Cancer) is called the Variables of Capricorn. The southern westerlies start somewhat south of South Africa. They tend to be stronger than the northern westerlies because they are mostly over water (roaring forties). The southern polar easterlies are mostly over Antarctica.

text: Seasonal shifts: All of the belts move north during the northern summer and south during the northern winter. Because global heating and cooling lags behind the position of the sun, they reach their northernmost latitude at or after the end of the northern summer. This brought the trade winds within reach of the Spain and Portugal and determined the sailing time of the Spanish treasure fleet. The northernmost position of the wind belts corresponds to the Atlantic hurricane season.

text: Land and sea breezes: Land gains and loses heat more rapidly than water. During the day, the land warms more rapidly than the water. The air above land warms, becomes thinner, and rises, drawing cooler air landward from the sea. At night, the process reverses, and cool heavy air from the land flows out to sea. These land and sea breezes are important along the coast.

text: Monsoon: The annual equivalent of the daily land and sea breezes is the yearly monsoon. During summer, the continents heat more rapidly than the oceans. Air over the continents warms, thins and rises drawing cooler moist ocean air landward, producing a wet season. During winter, the process reverses and cold, dry heavy air flows outward from the continents, producing a dry season. The monsoon is most striking in south Asia because of the size of the Eurasian landmass and because the Himalayas tend to bottle up the air above the continent. Approximations of the Indian monsoon exist in other places, but they are poorly developed.

text: Ocean Gyre: The fact that the westerlies and trade winds blow in opposite directions and that the continents prevent water from circling the globe contributes to the formation of circular ocean currents, clockwise in the northern hemisphere and counterclockwise in the southern hemisphere. The Coriolis force also plays a part. The trade winds push water west. At the doldrums it flows back east producing the equatorial countercurrent. See Ocean gyre.

text: Coriolis force, Hadley cell and other things: In the northern hemisphere, the Coriolis effect causes wind and water currents to bend to the right (clockwise). Cold heavy air flows south from the north pole and is bent west, forming the polar easterlies. Warm air rises at the equator drawing air from the north which bends to the west, contributing to the trade winds. The Coriolis effect bends the westerlies and trade winds slightly clockwise in the northern hemisphere.

text: Hot air rises at the doldrums. As it rises, it cools producing thunderstorms. The dry air flows north at a high altitude and descends at the horse latitudes and flows back to the equator with the trade winds. This is called the Hadley cell. There is also a Ferrel cell over the westerlies and a polar cell over the pole. There are other complexities, not all of which are properly understood.


document_title: OSI model

question_text: ipsec is defined at what layer of the osi model

root

text: OSI model

text: History[edit]

text: In the late 1970s, one project was administered by the International Organization for Standardization (ISO), while another was undertaken by the International Telegraph and Telephone Consultative Committee (CCITT, from French: Comité Consultatif International Téléphonique et Télégraphique). These two international standards bodies each developed a document that defined similar networking models.

tag: p

text: In 1983, these two documents were merged to form a standard called The Basic Reference Model for Open Systems Interconnection. The standard is usually referred to as the Open Systems Interconnection Reference Model, the OSI Reference Model, or simply the OSI model. It was published in 1984 by both the ISO, as standard ISO 7498, and the renamed CCITT (now called the Telecommunications Standardization Sector of the International Telecommunication Union or ITU-T) as standard X.200.

text: OSI had two major components, an abstract model of networking, called the Basic Reference Model or seven-layer model, and a set of specific protocols.

text: The concept of a seven-layer model was provided by the work of Charles Bachman at Honeywell Information Services. Various aspects of OSI design evolved from experiences with the ARPANET, NPLNET, EIN, CYCLADES network and the work in IFIP WG6.1. The new design was documented in ISO 7498 and its various addenda. In this model, a networking system was divided into layers. Within each layer, one or more entities implement its functionality. Each entity interacted directly only with the layer immediately beneath it, and provided facilities for use by the layer above it.

text: Protocols enable an entity in one host to interact with a corresponding entity at the same layer in another host. Service definitions abstractly described the functionality provided to an (N)-layer by an (N-1) layer, where N was one of the seven layers of protocols operating in the local host.

text: The OSI standards documents are available from the ITU-T as the X.200-series of recommendations.[1] Some of the protocol specifications were also available as part of the ITU-T X series. The equivalent ISO and ISO/IEC standards for the OSI model were available from ISO. Not all are free of charge.[2]

text: Description of OSI layers[edit]

text: The recommendation X.200 describes seven layers, labeled 1 to 7. Layer 1 is the lowest layer in this model.

text:
OSI Model

Layer
Protocol data unit (PDU)
Function[3]

Host
layers
7. Application
Data
High-level APIs, including resource sharing, remote file access

6. Presentation
Translation of data between a networking service and an application; including character encoding, data compression and encryption/decryption

5. Session
Managing communication sessions, i.e. continuous exchange of information in the form of multiple back-and-forth transmissions between two nodes

4. Transport
Segment (TCP) / Datagram (UDP)
Reliable transmission of data segments between points on a network, including segmentation, acknowledgement and multiplexing

Media
layers
3. Network
Packet
Structuring and managing a multi-node network, including addressing, routing and traffic control

2. Data link
Frame
Reliable transmission of data frames between two nodes connected by a physical layer

1. Physical
Bit
Transmission and reception of raw bit streams over a physical medium

tag: table

text: At each level N, two entities at the communicating devices (layer N peers) exchange protocol data units (PDUs) by means of a layer N protocol. Each PDU contains a payload, called the service data unit (SDU), along with protocol-related headers or footers.

text: Data processing by two communicating OSI-compatible devices is done as such:

text:
The data to be transmitted is composed at the topmost layer of the transmitting device (layer N) into a protocol data unit (PDU).
The PDU is passed to layer N-1, where it is known as the service data unit (SDU).
At layer N-1 the SDU is concatenated with a header, a footer, or both, producing a layer N-1 PDU. It is then passed to layer N-2.
The process continues until reaching the lowermost level, from which the data is transmitted to the receiving device.
At the receiving device the data is passed from the lowest to the highest layer as a series of SDUs while being successively stripped from each layer's header or footer, until reaching the topmost layer, where the last of the data is consumed.

tag: ol

text: Some orthogonal aspects, such as management and security, involve all of the layers (See ITU-T X.800 Recommendation[4]). These services are aimed at improving the CIA triad - confidentiality, integrity, and availability - of the transmitted data. In practice, the availability of a communication service is determined by the interaction between network design and network management protocols. Appropriate choices for both of these are needed to protect against denial of service.[citation needed]

text: Layer 1: Physical Layer[edit]

text: This section may need to be rewritten entirely to comply with Wikipedia's quality standards. You can help. The discussion page may contain suggestions. (August 2017)

text: The physical layer defines the electrical and physical specifications of the data connection. It defines the relationship between a device and a physical transmission medium (for example, an electrical cable, an optical fiber cable, or a radio frequency link). This includes the layout of pins, voltages, line impedance, cable specifications, signal timing and similar characteristics for connected devices and frequency (5 GHz or 2.4 GHz etc.) for wireless devices. It is responsible for transmission and reception of unstructured raw data in a physical medium. Bit rate control is done at the physical layer. It may define transmission mode as simplex, half duplex, and full duplex. It defines the network topology as bus, mesh, or ring being some of the most common.

text: The physical layer is the layer of low-level networking equipment, such as some hubs, cabling, and repeaters. The physical layer is never concerned with protocols or other such higher-layer items. Examples of hardware in this layer are network adapters, repeaters, network hubs, modems, and fiber media converters.

text: Layer 2: Data Link Layer[edit]

text: The data link layer provides node-to-node data transfer—a link between two directly connected nodes. It detects and possibly corrects errors that may occur in the physical layer. It defines the protocol to establish and terminate a connection between two physically connected devices. It also defines the protocol for flow control between them.

text: IEEE 802 divides the data link layer into two sublayers:[5]

text:
Medium access control (MAC) layer – responsible for controlling how devices in a network gain access to a medium and permission to transmit data.
Logical link control (LLC) layer – responsible for identifying and encapsulating network layer protocols, and controls error checking and frame synchronization.

tag: ul

text: The MAC and LLC layers of IEEE 802 networks such as 802.3 Ethernet, 802.11 Wi-Fi, and 802.15.4 ZigBee operate at the data link layer.

text: The Point-to-Point Protocol (PPP) is a data link layer protocol that can operate over several different physical layers, such as synchronous and asynchronous serial lines.

text: The ITU-T G.hn standard, which provides high-speed local area networking over existing wires (power lines, phone lines and coaxial cables), includes a complete data link layer that provides both error correction and flow control by means of a selective-repeat sliding-window protocol.

text: Layer 3: Network Layer[edit]

text: The network layer provides the functional and procedural means of transferring variable length data sequences (called datagrams) from one node to another connected in "different networks". A network is a medium to which many nodes can be connected, on which every node has an address and which permits nodes connected to it to transfer messages to other nodes connected to it by merely providing the content of a message and the address of the destination node and letting the network find the way to deliver the message to the destination node, possibly routing it through intermediate nodes. If the message is too large to be transmitted from one node to another on the data link layer between those nodes, the network may implement message delivery by splitting the message into several fragments at one node, sending the fragments independently, and reassembling the fragments at another node. It may, but does not need to, report delivery errors.

text: Message delivery at the network layer is not necessarily guaranteed to be reliable; a network layer protocol may provide reliable message delivery, but it need not do so.

text: A number of layer-management protocols, a function defined in the management annex, ISO 7498/4, belong to the network layer. These include routing protocols, multicast group management, network-layer information and error, and network-layer address assignment. It is the function of the payload that makes these belong to the network layer, not the protocol that carries them.[6]

text: Layer 4: Transport Layer[edit]

text: The transport layer provides the functional and procedural means of transferring variable-length data sequences from a source to a destination host, while maintaining the quality of service functions.

text: The transport layer controls the reliability of a given link through flow control, segmentation/desegmentation, and error control. Some protocols are state- and connection-oriented. This means that the transport layer can keep track of the segments and re-transmit those that fail delivery. The transport layer also provides the acknowledgement of the successful data transmission and sends the next data if no errors occurred. The transport layer creates packets out of the message received from the application layer. Packetizing is the process of dividing a long message into smaller messages.

text: OSI defines five classes of connection-mode transport protocols ranging from class 0 (which is also known as TP0 and provides the fewest features) to class 4 (TP4, designed for less reliable networks, similar to the Internet). Class 0 contains no error recovery, and was designed for use on network layers that provide error-free connections. Class 4 is closest to TCP, although TCP contains functions, such as the graceful close, which OSI assigns to the session layer. Also, all OSI TP connection-mode protocol classes provide expedited data and preservation of record boundaries. Detailed characteristics of TP0-4 classes are shown in the following table:[7]

text:
Feature name
TP0
TP1
TP2
TP3
TP4

Connection-oriented network
Yes
Yes
Yes
Yes
Yes

Connectionless network
No
No
No
No
Yes

Concatenation and separation
No
Yes
Yes
Yes
Yes

Segmentation and reassembly
Yes
Yes
Yes
Yes
Yes

Error recovery
No
Yes
Yes
Yes
Yes

Reinitiate connectiona
No
Yes
No
Yes
No

Multiplexing / demultiplexing over single virtual circuit
No
No
Yes
Yes
Yes

Explicit flow control
No
No
Yes
Yes
Yes

Retransmission on timeout
No
No
No
No
Yes

Reliable transport service
No
Yes
No
Yes
Yes

a If an excessive number of PDUs are unacknowledged.

text: An easy way to visualize the transport layer is to compare it with a post office, which deals with the dispatch and classification of mail and parcels sent. A post office inspects only the outer envelope of mail to determine its delivery. Higher layers may have the equivalent of double envelopes, such as cryptographic presentation services that can be read by the addressee only. Roughly speaking, tunneling protocols operate at the transport layer, such as carrying non-IP protocols such as IBM's SNA or Novell's IPX over an IP network, or end-to-end encryption with IPsec. While Generic Routing Encapsulation (GRE) might seem to be a network-layer protocol, if the encapsulation of the payload takes place only at endpoint, GRE becomes closer to a transport protocol that uses IP headers but contains complete frames or packets to deliver to an endpoint. L2TP carries PPP frames inside transport packet.

text: Although not developed under the OSI Reference Model and not strictly conforming to the OSI definition of the transport layer, the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP) of the Internet Protocol Suite are commonly categorized as layer-4 protocols within OSI.

text: Layer 5: Session Layer[edit]

text: The session layer controls the dialogues (connections) between computers. It establishes, manages and terminates the connections between the local and remote application. It provides for full-duplex, half-duplex, or simplex operation, and establishes checkpointing, adjournment, termination, and restart procedures. The OSI model made this layer responsible for graceful close of sessions, which is a property of the Transmission Control Protocol, and also for session checkpointing and recovery, which is not usually used in the Internet Protocol Suite. The session layer is commonly implemented explicitly in application environments that use remote procedure calls.

text: Layer 6: Presentation Layer[edit]

text: The presentation layer establishes context between application-layer entities, in which the application-layer entities may use different syntax and semantics if the presentation service provides a mapping between them. If a mapping is available, presentation service data units are encapsulated into session protocol data units and passed down the protocol stack.

text: This layer provides independence from data representation by translating between application and network formats. The presentation layer transforms data into the form that the application accepts. This layer formats data to be sent across a network. It is sometimes called the syntax layer.[8] The presentation layer can include compression functions.[9] The Presentation Layer negotiates the Transfer Syntax.

text: The original presentation structure used the Basic Encoding Rules of Abstract Syntax Notation One (ASN.1), with capabilities such as converting an EBCDIC-coded text file to an ASCII-coded file, or serialization of objects and other data structures from and to XML. ASN.1 effectively makes an application protocol invariant with respect to syntax.

text: Layer 7: Application Layer[edit]

text: The application layer is the OSI layer closest to the end user, which means both the OSI application layer and the user interact directly with the software application. This layer interacts with software applications that implement a communicating component. Such application programs fall outside the scope of the OSI model. Application-layer functions typically include identifying communication partners, determining resource availability, and synchronizing communication. When identifying communication partners, the application layer determines the identity and availability of communication partners for an application with data to transmit. The most important distinction in the application layer is the distinction between the application-entity and the application. For example, a reservation website might have two application-entities: one using HTTP to communicate with its users, and one for a remote database protocol to record reservations. Neither of these protocols have anything to do with reservations. That logic is in the application itself. The application layer per se has no means to determine the availability of resources in the network.

text: Cross-layer functions[edit]

text: Cross-layer functions are services that are not tied to a given layer, but may affect more than one layer. Examples include the following:

text:
Security service (telecommunication)[4] as defined by ITU-T X.800 recommendation.
Management functions, i.e. functions that permit to configure, instantiate, monitor, terminate the communications of two or more entities: there is a specific application-layer protocol, common management information protocol (CMIP) and its corresponding service, common management information service (CMIS), they need to interact with every layer in order to deal with their instances.
Multiprotocol Label Switching (MPLS) MPLS, ATM, and X.25 are 3a protocols. OSI divides the Network Layer into 3 roles: 3a) Subnetwork Access, 3b) Subnetwork Dependent Convergence and 3c) Subnetwork Independent Convergence. It was designed to provide a unified data-carrying service for both circuit-based clients and packet-switching clients which provide a datagram-based service model. It can be used to carry many different kinds of traffic, including IP packets, as well as native ATM, SONET, and Ethernet frames. Sometimes one sees reference to a Layer 2.5. This is a fiction create by those who are unfamiliar with the OSI Model and ISO 8648, Internal Organization of the Network Layer in particular.
ARP determines the mapping of an IPv4 address to the underlying MAC address. This is not a translation function. If it were IPv4 and the MAC address would be at the same layer. The implementation of the MAC protocol decodes the MAC PDU and delivers the User-Data to the IP-layer. Because Ethernet is a multi-access media, a device sending a PDU on an Ethernet segment needs to know what IP address maps to what MAC address.
DHCP, DHCP assigns IPv4 addresses to new systems joining a network. There is no means to derive or obtain an IPv4 address from an Ethernet address.
Domain Name Service is an Application Layer service which is used to look up the IP address of a given domain name. Once a reply is received from the DNS server, it is then possible to form a Layer 4 connection or flow to the desired host. There are no connections at Layer 3.
Cross MAC and PHY Scheduling is essential in wireless networks because of the time varying nature of wireless channels. By scheduling packet transmission only in favorable channel conditions, which requires the MAC layer to obtain channel state information from the PHY layer, network throughput can be significantly improved and energy waste can be avoided.[10]

text: Interfaces[edit]

text: Neither the OSI Reference Model nor OSI protocols specify any programming interfaces, other than deliberately abstract service specifications. Protocol specifications precisely define the interfaces between different computers, but the software interfaces inside computers, known as network sockets are implementation-specific.

text: For example, Microsoft Windows' Winsock, and Unix's Berkeley sockets and System V Transport Layer Interface, are interfaces between applications (layer 5 and above) and the transport (layer 4). NDIS and ODI are interfaces between the media (layer 2) and the network protocol (layer 3).

text: Interface standards, except for the physical layer to media, are approximate implementations of OSI service specifications.

text: Examples[edit]

text:
Layer
OSI protocols
TCP/IP protocols
Signaling
System 7[11]
AppleTalk
IPX
SNA
UMTS
Miscellaneous examples

No.
Name

7
Application

FTAM
X.400
X.500
DAP
ROSE
RTSE
ACSE[12]
CMIP[13]

INAP
MAP
TCAP
ISUP
TUP

AFP
ZIP
RTMP
NBP

SAP

APPC

HL7
Modbus

6
Presentation

ISO/IEC 8823
X.226

ISO/IEC 9576-1
X.236

MIME
SSL
TLS
XDR

AFP

TDI
ASCII
EBCDIC
MIDI
MPEG

5
Session

ISO/IEC 8327
X.225

ISO/IEC 9548-1
X.235

Sockets (session establishment in TCP / RTP / PPTP)

ASP
ADSP
PAP

NWLink

DLC?

Named pipes
NetBIOS
SAP
half duplex
full duplex
simplex
RPC
SOCKS

4
Transport

ISO/IEC 8073
TP0
TP1
TP2
TP3
TP4 (X.224)
ISO/IEC 8602
X.234

TCP
UDP
SCTP
DCCP

DDP
SPX

NBF

3
Network

ISO/IEC 8208
X.25 (PLP)

ISO/IEC 8878
X.223
ISO/IEC 8473-1
CLNP X.233
ISO/IEC 10589
IS-IS

IP
IPsec
ICMP
IGMP
OSPF
RIP

SCCP
MTP

ATP (TokenTalk / EtherTalk)

IPX

RRC / BMC

NBF
Q.931
NDP
IS-IS

2
Data link

ISO/IEC 7666
X.25 (LAPB)

Token Bus
X.222
ISO/IEC 8802-2
LLC (type 1 / 2)[14]

PPP
SBTV
SLIP

MTP
Q.710

LocalTalk
ARA
PPP

IEEE 802.3 framing
Ethernet II framing

SDLC

PDCP[15]
LLC
MAC

ARP
ARQ
ATM
Bit stuffing
CDP
CRC
DOCSIS
FDDI
FDP
Fibre Channel
Frame Relay
HDP
HDLC
IEEE 802.3 (Ethernet)
IEEE 802.11a/b/g/n (Ethernet MAC and LLC)
IEEE 802.1Q (VLAN)
ISL
ITU-T G.hn DLL
Linux interface bonding
PPP
Q.921
Token Ring

1
Physical

X.25 (X.21bis
EIA/TIA-232
EIA/TIA-449
EIA-530
G.703)[14]

MTP
Q.710

RS-232
RS-422
PhoneNet

Twinax

UMTS air interfaces

RS-232
Full duplex
RJ45 (8P8C)
V.35
V.34
I.430
I.431
T1
E1
10BASE-T
100BASE-TX
1000BASE-T
POTS
SONET
SDH
DSL
802.11a/b/g/n PHY
ITU-T G.hn PHY
CAN bus
DOCSIS
DWDM
OTN

text: Comparison with TCP/IP model[edit]

text: The design of protocols in the TCP/IP model of the Internet does not concern itself with strict hierarchical encapsulation and layering.[16] RFC 3439 contains a section entitled "Layering considered harmful".[17] TCP/IP does recognize four broad layers of functionality which are derived from the operating scope of their contained protocols: the scope of the software application; the end-to-end transport connection; the internetworking range; and the scope of the direct links to other nodes on the local network.[18]

text: Despite using a different concept for layering than the OSI model, these layers are often compared with the OSI layering scheme in the following way:

text:
The Internet application layer includes the OSI application layer, presentation layer, and most of the session layer.
Its end-to-end transport layer includes the graceful close function of the OSI session layer as well as the OSI transport layer.
The internetworking layer (Internet layer) is a subset of the OSI network layer.
The link layer includes the OSI data link layer and sometimes the physical layers, as well as some protocols of the OSI's network layer.

text: These comparisons are based on the original seven-layer protocol model as defined in ISO 7498, rather than refinements in such things as the internal organization of the network layer document.[citation needed]

text: The presumably strict layering of the OSI model as it is usually described does not present contradictions in TCP/IP, as it is permissible that protocol usage does not follow the hierarchy implied in a layered model. Such examples exist in some routing protocols (for example OSPF), or in the description of tunneling protocols, which provide a link layer for an application, although the tunnel host protocol might well be a transport or even an application-layer protocol in its own right.[citation needed]


document_title: DNA profiling

question_text: dna profiling is now made possible because of the work of

question_tokens: dna profiling is now made possible because of the work of

text: DNA profiling

text: Background[edit]

text: The modern process of DNA profiling was developed in 1984[5] by Sir Alec Jeffreys[6][7][8][9] while working in the Department of Genetics at the University of Leicester.[10]

text: Although 99.9% of human DNA sequences are the same in every person, enough of the DNA is different that it is possible to distinguish one individual from another, unless they are monozygotic ("identical") twins.[11] DNA profiling uses repetitive ("repeat") sequences that are highly variable,[11] called variable number tandem repeats (VNTRs), in particular short tandem repeats (STRs), also known as microsatellites, and minisatellites. VNTR loci are very similar between closely related individuals, but are so variable that unrelated individuals are extremely unlikely to have the same VNTRs.

text: DNA profiling process[edit]

text: Developed by Professor of Genetics Sir Alec Jeffreys,[12] the process begins with a sample of an individual's DNA (typically called a "reference sample"). A common method of collecting a reference sample is the use of a buccal swab, which is easy, non-invasive and cheap. When this is not available (e.g. because a court order is needed but not obtainable) other methods may need to be used to collect a sample of blood, saliva, semen, vaginal lubrication, or other appropriate fluid or tissue from personal items (e.g. a toothbrush, razor) or from stored samples (e.g. banked sperm or biopsy tissue). Samples obtained from blood relatives (related by birth, not marriage) can provide an indication of an individual's profile, as could human remains that had been previously profiled.

text: A reference sample is then analyzed to create the individual's DNA profile using one of a number of techniques, discussed below. The DNA profile is then compared against another sample to determine whether there is a genetic match.

text: RFLP analysis[edit]

text: The first methods for finding out genetics used for DNA profiling involved RFLP analysis. DNA is collected from cells, such as a blood sample, and cut into small pieces using a restriction enzyme (a restriction digest). This generates thousands of DNA fragments of differing sizes as a consequence of variations between DNA sequences of different individuals. The fragments are then separated on the basis of size using gel electrophoresis.

text: The separated fragments are then transferred to a nitrocellulose or nylon filter; this procedure is called a Southern blot. The DNA fragments within the blot are permanently fixed to the filter, and the DNA strands are denatured. Radiolabeled probe molecules are then added that are complementary to sequences in the genome that contain repeat sequences. These repeat sequences tend to vary in length among different individuals and are called variable number tandem repeat sequences or VNTRs. The probe molecules hybridize to DNA fragments containing the repeat sequences and excess probe molecules are washed away. The blot is then exposed to an X-ray film. Fragments of DNA that have bound to the probe molecules appear as fluoresent bands on the film.

text: The Southern blot technique is laborious, and requires large amounts of undegraded sample DNA. Also, Karl Brown's original technique looked at many minisatellite loci at the same time, increasing the observed variability, but making it hard to discern individual alleles (and thereby precluding paternity testing). These early techniques have been supplanted by PCR-based assays.

text: Polymerase chain reaction (PCR) analysis[edit]

text: Developed by Kary Mullis in 1983, a process was reported by which specific portions of the sample DNA can be amplified almost indefinitely (Saiki et al. 1985, 1988). This has revolutionized the whole field of DNA study. The process, polymerase chain reaction (PCR), mimics the biological process of DNA replication, but confines it to specific DNA sequences of interest. With the invention of the PCR technique, DNA profiling took huge strides forward in both discriminating power and the ability to recover information from very small (or degraded) starting samples.

text: PCR greatly amplifies the amounts of a specific region of DNA. In the PCR process, the DNA sample is denatured into the separate individual polynucleotide strands through heating. Two oligonucleotide DNA primers are used to hybridize to two corresponding nearby sites on opposite DNA strands in such a fashion that the normal enzymatic extension of the active terminal of each primer (that is, the 3’ end) leads toward the other primer. PCR uses replication enzymes that are tolerant of high temperatures, such as the thermostable Taq polymerase. In this fashion, two new copies of the sequence of interest are generated. Repeated denaturation, hybridization, and extension in this fashion produce an exponentially growing number of copies of the DNA of interest. Instruments that perform thermal cycling are readily available from commercial sources. This process can produce a million-fold or greater amplification of the desired region in 2 hours or less.

text: Early assays such as the HLA-DQ alpha reverse dot blot strips grew to be very popular due to their ease of use, and the speed with which a result could be obtained. However, they were not as discriminating as RFLP analysis. It was also difficult to determine a DNA profile for mixed samples, such as a vaginal swab from a sexual assault victim.

text: However, the PCR method was readily adaptable for analyzing VNTR, in particular STR loci. In recent years, research in human DNA quantitation has focused on new "real-time" quantitative PCR (qPCR) techniques. Quantitative PCR methods enable automated, precise, and high-throughput measurements. Inter-laboratory studies have demonstrated the importance of human DNA quantitation on achieving reliable interpretation of STR typing and obtaining consistent results across laboratories.

text: STR analysis[edit]

text: The system of DNA profiling used today is based on PCR and uses simple sequences[13] or short tandem repeats (STR). This method uses highly polymorphic regions that have short repeated sequences of DNA (the most common is 4 bases repeated, but there are other lengths in use, including 3 and 5 bases). Because unrelated people almost certainly have different numbers of repeat units, STRs can be used to discriminate between unrelated individuals. These STR loci (locations on a chromosome) are targeted with sequence-specific primers and amplified using PCR. The DNA fragments that result are then separated and detected using electrophoresis. There are two common methods of separation and detection, capillary electrophoresis (CE) and gel electrophoresis.

text: Each STR is polymorphic, but the number of alleles is very small. Typically each STR allele will be shared by around 5 - 20% of individuals. The power of STR analysis comes from looking at multiple STR loci simultaneously. The pattern of alleles can identify an individual quite accurately. Thus STR analysis provides an excellent identification tool. The more STR regions that are tested in an individual the more discriminating the test becomes.

text: From country to country, different STR-based DNA-profiling systems are in use. In North America, systems that amplify the CODIS 20[14] core loci are almost universal, whereas in the United Kingdom the DNA-17 17 loci system (which is compatible with The National DNA Database) is in use, and Australia uses 18 core markers.[15] Whichever system is used, many of the STR regions used are the same. These DNA-profiling systems are based on multiplex reactions, whereby many STR regions will be tested at the same time.

text: The true power of STR analysis is in its statistical power of discrimination. Because the 20 loci that are currently used for discrimination in CODIS are independently assorted (having a certain number of repeats at one locus does not change the likelihood of having any number of repeats at any other locus), the product rule for probabilities can be applied. This means that, if someone has the DNA type of ABC, where the three loci were independent, we can say that the probability of having that DNA type is the probability of having type A times the probability of having type B times the probability of having type C. This has resulted in the ability to generate match probabilities of 1 in a quintillion (1x1018) or more. However, DNA database searches showed much more frequent than expected false DNA profile matches.[16] Moreover, since there are about 12 million monozygotic twins on Earth, the theoretical probability is not accurate.

text: In practice, the risk of contaminated-matching is much greater than matching a distant relative, such as contamination of a sample from nearby objects, or from left-over cells transferred from a prior test. The risk is greater for matching the most common person in the samples: Everything collected from, or in contact with, a victim is a major source of contamination for any other samples brought into a lab. For that reason, multiple control-samples are typically tested in order to ensure that they stayed clean, when prepared during the same period as the actual test samples. Unexpected matches (or variations) in several control-samples indicates a high probability of contamination for the actual test samples. In a relationship test, the full DNA profiles should differ (except for twins), to prove that a person was not actually matched as being related to their own DNA in another sample.

text: AmpFLP[edit]

text: Another technique, AmpFLP, or amplified fragment length polymorphism was also put into practice during the early 1990s. This technique was also faster than RFLP analysis and used PCR to amplify DNA samples. It relied on variable number tandem repeat (VNTR) polymorphisms to distinguish various alleles, which were separated on a polyacrylamide gel using an allelic ladder (as opposed to a molecular weight ladder). Bands could be visualized by silver staining the gel. One popular focus for fingerprinting was the D1S80 locus. As with all PCR based methods, highly degraded DNA or very small amounts of DNA may cause allelic dropout (causing a mistake in thinking a heterozygote is a homozygote) or other stochastic effects. In addition, because the analysis is done on a gel, very high number repeats may bunch together at the top of the gel, making it difficult to resolve. AmpFLP analysis can be highly automated, and allows for easy creation of phylogenetic trees based on comparing individual samples of DNA. Due to its relatively low cost and ease of set-up and operation, AmpFLP remains popular in lower income countries.

text: DNA family relationship analysis[edit]

text: Using PCR technology, DNA analysis is widely applied to determine genetic family relationships such as paternity, maternity, siblingship and other kinships.

text: During conception, the father’s sperm cell and the mother’s egg cell, each containing half the amount of DNA found in other body cells, meet and fuse to form a fertilized egg, called a zygote. The zygote contains a complete set of DNA molecules, a unique combination of DNA from both parents. This zygote divides and multiplies into an embryo and later, a full human being.

text: At each stage of development, all the cells forming the body contain the same DNA—half from the father and half from the mother. This fact allows the relationship testing to use all types of all samples including loose cells from the cheeks collected using buccal swabs, blood or other types of samples.

text: There are predictable inheritance patterns at certain locations (called loci) in the human genome, which have been found to be useful in determining identity and biological relationships. These loci contain specific DNA markers that scientists use to identify individuals. In a routine DNA paternity test, the markers used are short tandem repeats (STRs), short pieces of DNA that occur in highly differential repeat patterns among individuals.

text: Each person’s DNA contains two copies of these markers—one copy inherited from the father and one from the mother. Within a population, the markers at each person’s DNA location could differ in length and sometimes sequence, depending on the markers inherited from the parents.

text: The combination of marker sizes found in each person makes up his/her unique genetic profile. When determining the relationship between two individuals, their genetic profiles are compared to see if they share the same inheritance patterns at a statistically conclusive rate.

text: For example, the following sample report from this commercial DNA paternity testing laboratory Universal Genetics signifies how relatedness between parents and child is identified on those special markers:

text:
DNA marker
Mother
Child
Alleged father

D21S11
28, 30
28, 31
29, 31

D7S820
9, 10
10, 11
11, 12

TH01
14, 15
14, 16
15, 16

D13S317
7, 8
7, 9
8, 9

D19S433
14, 16.2
14, 15
15, 17

text: The partial results indicate that the child and the alleged father’s DNA match among these five markers. The complete test results show this correlation on 16 markers between the child and the tested man to enable a conclusion to be drawn as to whether or not the man is the biological father.

text: Each marker is assigned with a Paternity Index (PI), which is a statistical measure of how powerfully a match at a particular marker indicates paternity. The PI of each marker is multiplied with each other to generate the Combined Paternity Index (CPI), which indicates the overall probability of an individual being the biological father of the tested child relative to a randomly selected man from the entire population of the same race. The CPI is then converted into a Probability of Paternity showing the degree of relatedness between the alleged father and child.

text: The DNA test report in other family relationship tests, such as grandparentage and siblingship tests, is similar to a paternity test report. Instead of the Combined Paternity Index, a different value, such as a Siblingship Index, is reported.

text: The report shows the genetic profiles of each tested person. If there are markers shared among the tested individuals, the probability of biological relationship is calculated to determine how likely the tested individuals share the same markers due to a blood relationship.

text: Y-chromosome analysis[edit]

text: Recent innovations have included the creation of primers targeting polymorphic regions on the Y-chromosome (Y-STR), which allows resolution of a mixed DNA sample from a male and female or cases in which a differential extraction is not possible. Y-chromosomes are paternally inherited, so Y-STR analysis can help in the identification of paternally related males. Y-STR analysis was performed in the Sally Hemings controversy to determine if Thomas Jefferson had sired a son with one of his slaves. The analysis of the Y-chromosome yields weaker results than autosomal chromosome analysis. The Y male sex-determining chromosome, as it is inherited only by males from their fathers, is almost identical along the patrilineal line. This leads to a less precise analysis than if autosomal chromosomes were testing, because of the random matching that occurs between pairs of chromosomes as zygotes are being made.[17]

text: Mitochondrial analysis[edit]

text: For highly degraded samples, it is sometimes impossible to get a complete profile of the 13 CODIS STRs. In these situations, mitochondrial DNA (mtDNA) is sometimes typed due to there being many copies of mtDNA in a cell, while there may only be 1-2 copies of the nuclear DNA. Forensic scientists amplify the HV1 and HV2 regions of the mtDNA, and then sequence each region and compare single-nucleotide differences to a reference. Because mtDNA is maternally inherited, directly linked maternal relatives can be used as match references, such as one's maternal grandmother's daughter's son. In general, a difference of two or more nucleotides is considered to be an exclusion. Heteroplasmy and poly-C differences may throw off straight sequence comparisons, so some expertise on the part of the analyst is required. mtDNA is useful in determining clear identities, such as those of missing people when a maternally linked relative can be found. mtDNA testing was used in determining that Anna Anderson was not the Russian princess she had claimed to be, Anastasia Romanov.

text: mtDNA can be obtained from such material as hair shafts and old bones/teeth. Control mechanism based on interaction point with data. This can be determined by tooled placement in sample.[citation needed]

text: DNA databases[edit]

text: An early application of a DNA database was the compilation of a Mitochondrial DNA Concordance,[18] prepared by Kevin W. P. Miller and John L. Dawson at the University of Cambridge from 1996 to 1998[19] from data collected as part of Miller's PhD thesis. There are now several DNA databases in existence around the world. Some are private, but most of the largest databases are government-controlled. The United States maintains the largest DNA database, with the Combined DNA Index System (CODIS) holding over 13 million records as of May 2018.[20] The United Kingdom maintains the National DNA Database (NDNAD), which is of similar size, despite the UK's smaller population. The size of this database, and its rate of growth, are giving concern to civil liberties groups in the UK, where police have wide-ranging powers to take samples and retain them even in the event of acquittal.[21] The Conservative–Liberal Democrat coalition partially addressed these concerns with part 1 of the Protection of Freedoms Act 2012, under which DNA samples must be deleted if suspects are acquitted or not charged, except in relation to certain (mostly serious and/or sexual) offences.

text: The U.S. Patriot Act of the United States provides a means for the U.S. government to get DNA samples from suspected terrorists. DNA information from crimes is collected and deposited into the CODIS database, which is maintained by the FBI. CODIS enables law enforcement officials to test DNA samples from crimes for matches within the database, providing a means of finding specific biological profiles associated with collected DNA evidence.[22]

text: When a match is made from a national DNA databank to link a crime scene to an offender having provided a DNA sample to a databank, that link is often referred to as a cold hit. A cold hit is of value in referring the police agency to a specific suspect but is of less evidential value than a DNA match made from outside the DNA Databank.[23]

text: FBI agents cannot legally store DNA of a person not convicted of a crime. DNA collected from a suspect not later convicted must be disposed of and not entered into the database. In 1998, a man residing in the UK was arrested on accusation of burglary. His DNA was taken and tested, and he was later released. Nine months later, this man's DNA was accidentally and illegally entered in the DNA database. New DNA is automatically compared to the DNA found at cold cases and, in this case, this man was found to be a match to DNA found at a rape and assault case one year earlier. The government then prosecuted him for these crimes. During the trial the DNA match was requested to be removed from the evidence because it had been illegally entered into the database. The request was carried out.[24]

text: The DNA collected from victims of rape is often stored for years until matched with the perpetrator's, usually when committing another crime. In 2014, Congress extended a bill that helps states deal with "a backlog" of unexamined evidence.[25]

text: Considerations when evaluating DNA evidence[edit]

text: In the early days of the use of genetic fingerprinting as criminal evidence, juries were often swayed by spurious statistical arguments by defense lawyers along these lines: Given a match that had a 1 in 5 million probability of occurring by chance, the lawyer would argue that this meant that in a country of say 60 million people there were 12 people who would also match the profile. This was then translated to a 1 in 12 chance of the suspect's being the guilty one. This argument is not sound unless the suspect was drawn at random from the population of the country. In fact, a jury should consider how likely it is that an individual matching the genetic profile would also have been a suspect in the case for other reasons. Also, different DNA analysis processes can reduce the amount of DNA recovery if the procedures are not properly done. Therefore, the number of times a piece of evidence is sampled can diminish the DNA collection efficiency. Another spurious statistical argument is based on the false assumption that a 1 in 5 million probability of a match automatically translates into a 1 in 5 million probability of innocence and is known as the prosecutor's fallacy.

text: When using RFLP, the theoretical risk of a coincidental match is 1 in 100 billion (100,000,000,000), although the practical risk is actually 1 in 1000 because monozygotic twins are 0.2% of the human population.[citation needed] Moreover, the rate of laboratory error is almost certainly higher than this, and often actual laboratory procedures do not reflect the theory under which the coincidence probabilities were computed. For example, the coincidence probabilities may be calculated based on the probabilities that markers in two samples have bands in precisely the same location, but a laboratory worker may conclude that similar—but not precisely identical—band patterns result from identical genetic samples with some imperfection in the agarose gel. However, in this case, the laboratory worker increases the coincidence risk by expanding the criteria for declaring a match. Recent studies have quoted relatively high error rates, which may be cause for concern.[26] In the early days of genetic fingerprinting, the necessary population data to accurately compute a match probability was sometimes unavailable. Between 1992 and 1996, arbitrary low ceilings were controversially put on match probabilities used in RFLP analysis rather than the higher theoretically computed ones.[27] Today, RFLP has become widely disused due to the advent of more discriminating, sensitive and easier technologies.

text: Since 1998, the DNA profiling system supported by The National DNA Database in the UK is the SGM+ DNA profiling system that includes 10 STR regions and a sex-indicating test. STRs do not suffer from such subjectivity and provide similar power of discrimination (1 in 1013 for unrelated individuals if using a full SGM+ profile). Figures of this magnitude are not considered to be statistically supportable by scientists in the UK; for unrelated individuals with full matching DNA profiles a match probability of 1 in a billion is considered statistically supportable. However, with any DNA technique, the cautious juror should not convict on genetic fingerprint evidence alone if other factors raise doubt. Contamination with other evidence (secondary transfer) is a key source of incorrect DNA profiles and raising doubts as to whether a sample has been adulterated is a favorite defense technique. More rarely, chimerism is one such instance where the lack of a genetic match may unfairly exclude a suspect.

text: Evidence of genetic relationship[edit]

text: It is possible to use DNA profiling as evidence of genetic relationship, although such evidence varies in strength from weak to positive. Testing that shows no relationship is absolutely certain. Further, while almost all individuals have a single and distinct set of genes, ultra-rare individuals, known as "chimeras", have at least two different sets of genes. There have been two cases of DNA profiling that falsely suggested that a mother was unrelated to her children.[28] This happens when two eggs are fertilized at the same time and fuse together to create one individual instead of twins.

text: Fake DNA evidence[edit]

text: In one case, a criminal planted fake DNA evidence in his own body: John Schneeberger raped one of his sedated patients in 1992 and left semen on her underwear. Police drew what they believed to be Schneeberger's blood and compared its DNA against the crime scene semen DNA on three occasions, never showing a match. It turned out that he had surgically inserted a Penrose drain into his arm and filled it with foreign blood and anticoagulants.

text: The functional analysis of genes and their coding sequences (open reading frames [ORFs]) typically requires that each ORF be expressed, the encoded protein purified, antibodies produced, phenotypes examined, intracellular localization determined, and interactions with other proteins sought.[29] In a study conducted by the life science company Nucleix and published in the journal Forensic Science International, scientists found that an in vitro synthesized sample of DNA matching any desired genetic profile can be constructed using standard molecular biology techniques without obtaining any actual tissue from that person. Nucleix claims they can also prove the difference between non-altered DNA and any that was synthesized.[30]

text: In the case of the Phantom of Heilbronn, police detectives found DNA traces from the same woman on various crime scenes in Austria, Germany, and France—among them murders, burglaries and robberies. Only after the DNA of the "woman" matched the DNA sampled from the burned body of a male asylum seeker in France did detectives begin to have serious doubts about the DNA evidence. It was eventually discovered that DNA traces were already present on the cotton swabs used to collect the samples at the crime scene, and the swabs had all been produced at the same factory in Austria. The company's product specification said that the swabs were guaranteed to be sterile, but not DNA-free.

text: DNA evidence as evidence in criminal trials[edit]

text:
Evidence

Part of the common law series

Types of evidence

Testimony
Documentary
Real (physical)
Digital
Exculpatory
Inculpatory
Demonstrative
Eyewitness identification
Genetic (DNA)
Lies

Relevance

Burden of proof
Laying a foundation
Materiality
Public policy exclusions
Spoliation
Character
Habit
Similar fact

Authentication

Chain of custody
Judicial notice
Best evidence rule
Self-authenticating document
Ancient document
Hague Evidence Convention

Witnesses

Competence
Privilege
Direct examination
Cross-examination
Redirect
Impeachment
Recorded recollection
Expert witness
Dead Man's Statute

Hearsay and exceptions

in English law
in United States law
Confessions
Business records
Excited utterance
Dying declaration
Party admission
Ancient document
Declaration against interest
Present sense impression
Res gestae
Learned treatise
Implied assertion

Other common law areas

Contract
Tort
Property
Wills, trusts and estates
Criminal law

v
t
e

text: Familial DNA searching[edit]

text: Familial DNA searching (sometimes referred to as "familial DNA" or "familial DNA database searching") is the practice of creating new investigative leads in cases where DNA evidence found at the scene of a crime (forensic profile) strongly resembles that of an existing DNA profile (offender profile) in a state DNA database but there is not an exact match.[31][32] After all other leads have been exhausted, investigators may use specially developed software to compare the forensic profile to all profiles taken from a state's DNA database to generate a list of those offenders already in the database who are most likely to be a very close relative of the individual whose DNA is in the forensic profile.[33] To eliminate the majority of this list when the forensic DNA is a man's, crime lab technicians conduct Y-STR analysis. Using standard investigative techniques, authorities are then able to build a family tree. The family tree is populated from information gathered from public records and criminal justice records. Investigators rule out family members' involvement in the crime by finding excluding factors such as sex, living out of state or being incarcerated when the crime was committed. They may also use other leads from the case, such as witness or victim statements, to identify a suspect. Once a suspect has been identified, investigators seek to legally obtain a DNA sample from the suspect. This suspect DNA profile is then compared to the sample found at the crime scene to definitively identify the suspect as the source of the crime scene DNA.

text: Familial DNA database searching was first used in an investigation leading to the conviction of Jeffrey Gafoor of the murder of Lynette White in the United Kingdom on 4 July 2003. DNA evidence was matched to Gafoor's nephew, who at 14 years old had not been born at the time of the murder in 1988. It was used again in 2004[34] to find a man who threw a brick from a motorway bridge and hit a lorry driver, killing him. DNA found on the brick matched that found at the scene of a car theft earlier in the day, but there were no good matches on the national DNA database. A wider search found a partial match to an individual; on being questioned, this man revealed he had a brother, Craig Harman, who lived very close to the original crime scene. Harman voluntarily submitted a DNA sample, and confessed when it matched the sample from the brick.[35] Currently, familial DNA database searching is not conducted on a national level in the United States, where states determine how and when to conduct familial searches. The first familial DNA search with a subsequent conviction in the United States was conducted in Denver, Colorado, in 2008, using software developed under the leadership of Denver District Attorney Mitch Morrissey and Denver Police Department Crime Lab Director Gregg LaBerge.[36] California was the first state to implement a policy for familial searching under then Attorney General, now Governor, Jerry Brown.[37] In his role as consultant to the Familial Search Working Group of the California Department of Justice, former Alameda County Prosecutor Rock Harmon is widely considered to have been the catalyst in the adoption of familial search technology in California. The technique was used to catch the Los Angeles serial killer known as the "Grim Sleeper" in 2010.[38] It wasn't a witness or informant that tipped off law enforcement to the identity of the "Grim Sleeper" serial killer, who had eluded police for more than two decades, but DNA from the suspect's own son. The suspect's son had been arrested and convicted in a felony weapons charge and swabbed for DNA the year before. When his DNA was entered into the database of convicted felons, detectives were alerted to a partial match to evidence found at the "Grim Sleeper" crime scenes. David Franklin Jr., also known as the Grim Sleeper, was charged with ten counts of murder and one count of attempted murder.[39] More recently, familial DNA led to the arrest of 21-year-old Elvis Garcia on charges of sexual assault and false imprisonment of a woman in Santa Cruz in 2008.[40] In March 2011 Virginia Governor Bob McDonnell announced that Virginia would begin using familial DNA searches.[41] Other states are expected to follow.

text: At a press conference in Virginia on March 7, 2011, regarding the East Coast Rapist, Prince William County prosecutor Paul Ebert and Fairfax County Police Detective John Kelly said the case would have been solved years ago if Virginia had used familial DNA searching. Aaron Thomas, the suspected East Coast Rapist, was arrested in connection with the rape of 17 women from Virginia to Rhode Island, but familial DNA was not used in the case.[42]

text: Critics of familial DNA database searches argue that the technique is an invasion of an individual's 4th Amendment rights.[43] Privacy advocates are petitioning for DNA database restrictions, arguing that the only fair way to search for possible DNA matches to relatives of offenders or arrestees would be to have a population-wide DNA database.[24] Some scholars have pointed out that the privacy concerns surrounding familial searching are similar in some respects to other police search techniques,[44] and most have concluded that the practice is constitutional.[45] The Ninth Circuit Court of Appeals in United States v. Pool (vacated as moot) suggested that this practice is somewhat analogous to a witness looking at a photograph of one person and stating that it looked like the perpetrator, which leads law enforcement to show the witness photos of similar looking individuals, one of whom is identified as the perpetrator.[46] Regardless of whether familial DNA searching was the method used to identify the suspect, authorities always conduct a normal DNA test to match the suspect's DNA with that of the DNA left at the crime scene.

text: Critics also claim that racial profiling could occur on account of familial DNA testing. In the United States, the conviction rates of racial minorities are much higher than that of the overall population. It is unclear whether this is due to discrimination from police officers and the courts, as opposed to a simple higher rate of offence among minorities. Arrest-based databases, which are found in the majority of the United States, lead to an even greater level of racial discrimination. An arrest, as opposed to conviction, relies much more heavily on police discretion.[24]

text: For instance, investigators with Denver District Attorney's Office successfully identified a suspect in a property theft case using a familial DNA search. In this example, the suspect's blood left at the scene of the crime strongly resembled that of a current Colorado Department of Corrections prisoner.[47] Using publicly available records, the investigators created a family tree. They then eliminated all the family members who were incarcerated at the time of the offense, as well as all of the females (the crime scene DNA profile was that of a male). Investigators obtained a court order to collect the suspect's DNA, but the suspect actually volunteered to come to a police station and give a DNA sample. After providing the sample, the suspect walked free without further interrogation or detainment. Later confronted with an exact match to the forensic profile, the suspect pleaded guilty to criminal trespass at the first court date and was sentenced to two years probation.

text: In Italy a familiar DNA search has been done to solve the case of the murder of Yara Gambirasio whose body was found in the bush[clarification needed] three months after her disappearance. A DNA trace was found on the underwear of the murdered teenage near and a DNA sample was requested from a person who lived near the municipality of Brembate di Sopra and a common male ancestor was found in the DNA sample of a young man not involved in the murder. After a long investigation the father of the supposed killer was identified as Giuseppe Guerinoni, a deceased man, but his two sons born from his wife were not related to the DNA samples found on the body of Yara. After three and a half years the DNA found on the underwear of the deceased girl was matched with Massimo Giuseppe Bosetti who was arrested and accused of the murder of the 13-year-old girl.In the summer of 2016 Bosetti was found guilty and sentenced to life by the Corte d'assise of Bergamo.

text: Partial matches[edit]

text: Partial DNA matches are not searches[clarification needed] themselves, but are the result of moderate stringency CODIS searches that produce a potential match that shares at least one allele at every locus.[48] Partial matching does not involve the use of familial search software, such as those used in the UK and United States, or additional Y-STR analysis, and therefore often misses sibling relationships. Partial matching has been used to identify suspects in several cases in the UK and United States,[49] and has also been used as a tool to exonerate the falsely accused. Darryl Hunt was wrongly convicted in connection with the rape and murder of a young woman in 1984 in North Carolina.[50] Hunt was exonerated in 2004 when a DNA database search produced a remarkably close match between a convicted felon and the forensic profile from the case. The partial match led investigators to the felon’s brother, Willard E. Brown, who confessed to the crime when confronted by police. A judge then signed an order to dismiss the case against Hunt. In Italy, partial matching has been used in the controversial murder of Yara Gambirasio, a child found dead about a month after her presumed kidnapping. In this case, the partial match has been used as the only incriminating element against the defendant, Massimo Bossetti, who has been subsequently condemned for the murder (waiting appeal by the Italian Supreme Court).

text: Surreptitious DNA collecting[edit]

text: Police forces may collect DNA samples without a suspect's knowledge, and use it as evidence. The legality of the practice has been questioned in Australia.[citation needed]

text: In the United States, it has been accepted, courts often ruling that there is no expectation of privacy, citing California v. Greenwood (1988), in which the Supreme Court held that the Fourth Amendment does not prohibit the warrantless search and seizure of garbage left for collection outside the curtilage of a home. Critics of this practice underline that this analogy ignores that "most people have no idea that they risk surrendering their genetic identity to the police by, for instance, failing to destroy a used coffee cup. Moreover, even if they do realize it, there is no way to avoid abandoning one's DNA in public."[51]

text: The United States Supreme Court ruled in Maryland v. King (2013) that DNA sampling of prisoners arrested for serious crimes is constitutional.[52][53][54]

text: In the UK, the Human Tissue Act 2004 prohibits private individuals from covertly collecting biological samples (hair, fingernails, etc.) for DNA analysis, but exempts medical and criminal investigations from the prohibition.[55]

text: England and Wales[edit]

text: Evidence from an expert who has compared DNA samples must be accompanied by evidence as to the sources of the samples and the procedures for obtaining the DNA profiles.[56] The judge must ensure that the jury must understand the significance of DNA matches and mismatches in the profiles. The judge must also ensure that the jury does not confuse the match probability (the probability that a person that is chosen at random has a matching DNA profile to the sample from the scene) with the probability that a person with matching DNA committed the crime. In 1996 R v. Doheny[57] Phillips LJ gave this example of a summing up, which should be carefully tailored to the particular facts in each case:

text: Members of the Jury, if you accept the scientific evidence called by the Crown, this indicates that there are probably only four or five white males in the United Kingdom from whom that semen stain could have come. The Defendant is one of them. If that is the position, the decision you have to reach, on all the evidence, is whether you are sure that it was the Defendant who left that stain or whether it is possible that it was one of that other small group of men who share the same DNA characteristics.

text: Juries should weigh up conflicting and corroborative evidence, using their own common sense and not by using mathematical formulae, such as Bayes' theorem, so as to avoid "confusion, misunderstanding and misjudgment".[58]

text: Presentation and evaluation of evidence of partial or incomplete DNA profiles[edit]

text: In R v Bates,[59] Moore-Bick LJ said:

text: We can see no reason why partial profile DNA evidence should not be admissible provided that the jury are made aware of its inherent limitations and are given a sufficient explanation to enable them to evaluate it. There may be cases where the match probability in relation to all the samples tested is so great that the judge would consider its probative value to be minimal and decide to exclude the evidence in the exercise of his discretion, but this gives rise to no new question of principle and can be left for decision on a case by case basis. However, the fact that there exists in the case of all partial profile evidence the possibility that a "missing" allele might exculpate the accused altogether does not provide sufficient grounds for rejecting such evidence. In many there is a possibility (at least in theory) that evidence that would assist the accused and perhaps even exculpate him altogether exists, but that does not provide grounds for excluding relevant evidence that is available and otherwise admissible, though it does make it important to ensure that the jury are given sufficient information to enable them to evaluate that evidence properly.[60]

text: DNA testing in the United States[edit]

text: There are state laws on DNA profiling in all 50 states of the United States.[61] Detailed information on database laws in each state can be found at the National Conference of State Legislatures website.[62]

text: Development of artificial DNA[edit]

text: In August 2009, scientists in Israel raised serious doubts concerning the use of DNA by law enforcement as the ultimate method of identification. In a paper published in the journal Forensic Science International: Genetics, the Israeli researchers demonstrated that it is possible to manufacture DNA in a laboratory, thus falsifying DNA evidence. The scientists fabricated saliva and blood samples, which originally contained DNA from a person other than the supposed donor of the blood and saliva.[63]

text: The researchers also showed that, using a DNA database, it is possible to take information from a profile and manufacture DNA to match it, and that this can be done without access to any actual DNA from the person whose DNA they are duplicating. The synthetic DNA oligos required for the procedure are common in molecular laboratories.[63]

text: The New York Times quoted the lead author, Daniel Frumkin, saying, "You can just engineer a crime scene ... any biology undergraduate could perform this".[63] Frumkin perfected a test that can differentiate real DNA samples from fake ones. His test detects epigenetic modifications, in particular, DNA methylation[64]. Seventy percent of the DNA in any human genome is methylated, meaning it contains methyl group modifications within a CpG dinucleotide context. Methylation at the promoter region is associated with gene silencing. The synthetic DNA lacks this epigenetic modification, which allows the test to distinguish manufactured DNA from genuine DNA.[63]

text: It is unknown how many police departments, if any, currently use the test. No police lab has publicly announced that it is using the new test to verify DNA results.[65]

text: Cases[edit]

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In 1986, Richard Buckland was exonerated, despite having admitted to the rape and murder of a teenager near Leicester, the city where DNA profiling was first developed. This was the first use of DNA fingerprinting in a criminal investigation, and the first to prove a suspect's innocence.[66] The following year Colin Pitchfork was identified as the perpetrator of the same murder, in addition to another, using the same techniques that had cleared Buckland.[67]
In 1987, genetic fingerprinting was used in criminal court for the first time in the trial of a man accused of unlawful intercourse with a mentally handicapped 14-year-old female who gave birth to a baby.[68]
In 1987, Florida rapist Tommie Lee Andrews was the first person in the United States to be convicted as a result of DNA evidence, for raping a woman during a burglary; he was convicted on November 6, 1987, and sentenced to 22 years in prison.[69][70]
In 1988, Timothy Wilson Spencer was the first man in Virginia to be sentenced to death through DNA testing, for several rape and murder charges. He was dubbed "The South Side Strangler" because he killed victims on the south side of Richmond, Virginia. He was later charged with rape and first-degree murder and was sentenced to death. He was executed on April 27, 1994. David Vasquez, initially convicted of one of Spencer's crimes, became the first man in America exonerated based on DNA evidence.
In 1989, Chicago man Gary Dotson was the first person whose conviction was overturned using DNA evidence.
In 1991, Allan Legere was the first Canadian to be convicted as a result of DNA evidence, for four murders he had committed while an escaped prisoner in 1989. During his trial, his defense argued that the relatively shallow gene pool of the region could lead to false positives.
In 1992, DNA evidence was used to prove that Nazi doctor Josef Mengele was buried in Brazil under the name Wolfgang Gerhard.
In 1992, DNA from a palo verde tree was used to convict Mark Alan Bogan of murder. DNA from seed pods of a tree at the crime scene was found to match that of seed pods found in Bogan's truck. This is the first instance of plant DNA admitted in a criminal case.[71][72][73]
In 1993, Kirk Bloodsworth was the first person to have been convicted of murder and sentenced to death, whose conviction was overturned using DNA evidence.
The 1993 rape and murder of Mia Zapata, lead singer for the Seattle punk band The Gits, was unsolved nine years after the murder. A database search in 2001 failed, but the killer's DNA was collected when he was arrested in Florida for burglary and domestic abuse in 2002.
The science was made famous in the United States in 1994 when prosecutors heavily relied on DNA evidence allegedly linking O. J. Simpson to a double murder. The case also brought to light the laboratory difficulties and handling procedure mishaps that can cause such evidence to be significantly doubted.
In 1994, Royal Canadian Mounted Police (RCMP) detectives successfully tested hairs from a cat known as Snowball, and used the test to link a man to the murder of his wife, thus marking for the first time in forensic history the use of non-human animal DNA to identify a criminal (plant DNA was used in 1992, see above).
In 1994, the claim that Anna Anderson was Grand Duchess Anastasia Nikolaevna of Russia was tested after her death using samples of her tissue that had been stored at a Charlottesville, Virginia hospital following a medical procedure. The tissue was tested using DNA fingerprinting, and showed that she bore no relation to the Romanovs.[74]
In 1994, Earl Washington, Jr., of Virginia had his death sentence commuted to life imprisonment a week before his scheduled execution date based on DNA evidence. He received a full pardon in 2000 based on more advanced testing.[75] His case is often cited by opponents of the death penalty.
In 1995, the British Forensic Science Service carried out its first mass intelligence DNA screening in the investigation of the Naomi Smith murder case.
In 1998, Richard J. Schmidt was convicted of attempted second-degree murder when it was shown that there was a link between the viral DNA of the human immunodeficiency virus (HIV) he had been accused of injecting in his girlfriend and viral DNA from one of his patients with AIDS. This was the first time viral DNA fingerprinting had been used as evidence in a criminal trial.
In 1999, Raymond Easton, a disabled man from Swindon, England, was arrested and detained for seven hours in connection with a burglary. He was released due to an inaccurate DNA match. His DNA had been retained on file after an unrelated domestic incident some time previously.[76]
In 2000 Frank Lee Smith was proved innocent by DNA profiling of the murder of an eight-year-old girl after spending 14 years on death row in Florida, USA. However he had died of cancer just before his innocence was proven.[77] In view of this the Florida state governor ordered that in future any death row inmate claiming innocence should have DNA testing.[75]
In May 2000 Gordon Graham murdered Paul Gault at his home in Lisburn, Northern Ireland. Graham was convicted of the murder when his DNA was found on a sports bag left in the house as part of an elaborate ploy to suggest the murder occurred after a burglary had gone wrong. Graham was having an affair with the victim's wife at the time of the murder. It was the first time Low Copy Number DNA was used in Northern Ireland.[78]
In 2001, Wayne Butler was convicted for the murder of Celia Douty. It was the first murder in Australia to be solved using DNA profiling.[79][80]
In 2002, the body of James Hanratty, hanged in 1962 for the "A6 murder", was exhumed and DNA samples from the body and members of his family were analysed. The results convinced Court of Appeal judges that Hanratty's guilt, which had been strenuously disputed by campaigners, was proved "beyond doubt".[81] Paul Foot and some other campaigners continued to believe in Hanratty's innocence and argued that the DNA evidence could have been contaminated, noting that the small DNA samples from items of clothing, kept in a police laboratory for over 40 years "in conditions that do not satisfy modern evidential standards", had had to be subjected to very new amplification techniques in order to yield any genetic profile.[82] However, no DNA other than Hanratty's was found on the evidence tested, contrary to what would have been expected had the evidence indeed been contaminated.[83]
In 2002, DNA testing was used to exonerate Douglas Echols, a man who was wrongfully convicted in a 1986 rape case. Echols was the 114th person to be exonerated through post-conviction DNA testing.
In August 2002, Annalisa Vincenzi was shot dead in Tuscany. Bartender Peter Hamkin, 23, was arrested, in Merseyside in March 2003 on an extradition warrant heard at Bow Street Magistrates' Court in London to establish whether he should be taken to Italy to face a murder charge. DNA "proved" he shot her, but he was cleared on other evidence.[84]
In 2003, Welshman Jeffrey Gafoor was convicted of the 1988 murder of Lynette White, when crime scene evidence collected 12 years earlier was re-examined using STR techniques, resulting in a match with his nephew.[85] This may be the first known example of the DNA of an innocent yet related individual being used to identify the actual criminal, via "familial searching".
In March 2003, Josiah Sutton was released from prison after serving four years of a twelve-year sentence for a sexual assault charge. Questionable DNA samples taken from Sutton were retested in the wake of the Houston Police Department's crime lab scandal of mishandling DNA evidence.
In June 2003, because of new DNA evidence, Dennis Halstead, John Kogut and John Restivo won a re-trial on their murder conviction, their convictions were struck down and they were released.[86] The three men had already served eighteen years of their thirty-plus-year sentences.
The trial of Robert Pickton (convicted in December 2003) is notable in that DNA evidence is being used primarily to identify the victims, and in many cases to prove their existence.
In 2004, DNA testing shed new light into the mysterious 1912 disappearance of Bobby Dunbar, a four-year-old boy who vanished during a fishing trip. He was allegedly found alive eight months later in the custody of William Cantwell Walters, but another woman claimed that the boy was her son, Bruce Anderson, whom she had entrusted in Walters' custody. The courts disbelieved her claim and convicted Walters for the kidnapping. The boy was raised and known as Bobby Dunbar throughout the rest of his life. However, DNA tests on Dunbar's son and nephew revealed the two were not related, thus establishing that the boy found in 1912 was not Bobby Dunbar, whose real fate remains unknown.[87]
In 2005, Gary Leiterman was convicted of the 1969 murder of Jane Mixer, a law student at the University of Michigan, after DNA found on Mixer's pantyhose was matched to Leiterman. DNA in a drop of blood on Mixer's hand was matched to John Ruelas, who was only four years old in 1969 and was never successfully connected to the case in any other way. Leiterman's defense unsuccessfully argued that the unexplained match of the blood spot to Ruelas pointed to cross-contamination and raised doubts about the reliability of the lab's identification of Leiterman.[88][89][90]
In December 2005, Evan Simmons was proven innocent of a 1981 attack on an Atlanta woman after serving twenty-four years in prison. Mr. Clark is the 164th person in the United States and the fifth in Georgia to be freed using post-conviction DNA testing.
In November 2008, Anthony Curcio was arrested for masterminding one of the most elaborately planned armored car heists in history. DNA evidence linked Curcio to the crime.[91]
In March 2009, Sean Hodgson—convicted of 1979 killing of Teresa De Simone, 22, in her car in Southampton—was released after tests proved DNA from the scene was not his. It was later matched to DNA retrieved from the exhumed body of David Lace. Lace had previously confessed to the crime but was not believed by the detectives. He served time in prison for other crimes committed at the same time as the murder and then committed suicide in 1988.[92]
In 2012, familial DNA profiling led to Alice Collins Plebuch's unexpected discovery that her ancestral bloodline was not purely Irish, as she had previously been led to believe, but that her heritage also contained European Jewish, Middle Eastern and Eastern European. This led her into an extensive genealogy investigation which resulted in her uncovering the genetic family of her adopted father.[93][94]
In 2016 Anthea Ring, abandoned as baby, was able to use a DNA sample and DNA matching database to discover her deceased mother’s identity and roots in County Mayo, Ireland. A recently developed forensic test was subsequently used to capture DNA from saliva left on old stamps and envelopes by her suspected father, uncovered through painstaking genealogy research. The DNA in the first three samples was too degraded to use. However, on the fourth, more than enough DNA was found. The test, which has a degree of accuracy acceptable in UK courts, proved that a man named Patrick Coyne was her biological father.[95][96]

text: DNA evidence as evidence to prove rights of succession to British titles[edit]

text: DNA testing is used to establish the right of succession to British titles.[97]

text: Cases:

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Baron Moynihan
Pringle baronets