Genetic fingerprinting 44290 225094127 2008-07-11T21:12:54Z RussBot 279219 Robot-assisted fix [[WP:DPL|links to disambiguation page]] America [[Image:D1S80Demo.gif|thumb|right|350px|<center>Variations of VNTR allele lengths in 6 individuals.</center>]] '''Genetic fingerprinting''' (also called '''DNA testing''', '''DNA typing''', or '''DNA profiling''') is a technique used to distinguish between individuals of the same species using only samples of their [[DNA]]. Although two individuals will have the vast majority of their DNA sequence in common, DNA profiling exploits highly variable repeat sequences called [[Variable number tandem repeats|VNTR]]s. These [[Locus (genetics)|loci]] are variable enough that two unrelated humans are unlikely to have the same [[allele]]s. The technique was first reported in 1984 by Dr. [[Alec Jeffreys]] at the [[University of Leicester]]<ref>Jeffreys A.J., Wilson V., Thein S.W. (1985). [http://www.nature.com/nature/journal/v314/n6006/abs/314067a0.html "Hypervariable 'minisatellite' regions in human DNA"]. Nature 314: 67-73. doi:10.1038/314067a0</ref>, and is now the basis of several [[National DNA database|national DNA identification databases]]. ==Reference samples== DNA identification must be done by an extraction of DNA from substances such as: * Personal items (e.g. toothbrush, razor, ...) * Banked samples (e.g. banked [[spermatozoon|sperm]] or [[biopsy]] tissue) * Blood kin (biological relative) * Human remains previously identified Reference samples are often collected using [[mouth|buccal]] [[swab]]. {{ForensicScience}} ==DNA fingerprinting methods== DNA fingerprinting begins by extracting DNA from the cells in a sample of blood, saliva, semen, or other appropriate fluid or tissue. ===RFLP analysis=== {{main|Restriction fragment length polymorphism}} The first methods used for DNA fingerprinting involved [[restriction enzyme]] digestion, followed by [[Southern blot]] analysis. Although [[polymorphism]]s can exist in the restriction enzyme cleavage sites, more commonly the enzymes and DNA probes were used to analyze VNTR loci. However, the Southern blot technique is laborious, and requires large amounts of undegraded sample DNA. Also, Jeffreys' original technique looked at many [[minisatellite]] loci at the same time, increasing the observed variablitiy, but making it hard to discern individual alleles (and thereby precluding [[parental testing]]). These early techniques have been supplanted by [[polymerase chain reaction|PCR]]-based assays. ===PCR analysis=== :''Main article: [[polymerase chain reaction]]'' With the invention of the [[polymerase chain reaction]] (PCR) technique, DNA fingerprinting took huge strides forward in both discriminating power and the ability to recover information from very small (or degraded) starting samples. PCR greatly amplifies the amounts of a specific region of DNA, using [[oligonucleotide]] [[Primer (molecular biology)|primers]] and a [[Taq polymerase|thermostable DNA polymerase]]. Early assays such as the [[Human leukocyte antigen|HLA]]-[[HLA-DQA1|DQ alpha]] [[Allele specific oligonucleotide|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. It was also difficult to determine a DNA profile for mixed samples, such as a vaginal swab from a sexual assault victim. Fortunately, the PCR method is readily adaptable for analyzing VNTR loci. In the [[United States]] the [[Federal Bureau of Investigation|FBI]] has standardized a set of 13 VNTR assays for DNA typing, and has organized the [[Combined DNA Index System|CODIS]] database for forensic identification in criminal cases. Similar assays and [[National DNA database|databases]] have been set up in other countries. Also, commercial kits are available that analyze [[single nucleotide polymorphisms]] (SNPs). These kits use PCR to amplify specific regions with known variations and hybridize them to [[Allele specific oligonucleotide|probes]] anchored on cards, which results in a colored spot corresponding to the particular sequence variation. ===STR analysis=== {{main|Short tandem repeats}} The most prevalent method of DNA fingerprinting used today is based on PCR and uses 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 different people have different numbers of repeat units, these regions of DNA can be used to discriminate between individuals. These STR loci (locations) are targeted with sequence-specific primers and are 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]]. The polymorphisms displayed at each STR region are by themselves very common, typically each polymorphism will be shared by around 5 - 20% of individuals. When looking at multiple loci, it is the unique combination of these polymorphisms to an individual that makes this method discriminating as an identification tool. The more STR regions that are tested in an individual the more discriminating the test becomes. From country to country, different STR-based DNA-profiling systems are in use. In North America systems which amplify the [[CODIS]] 13 core loci are almost universal, while in the UK the SGM+ system, which is compatible with The [[National DNA Database]] in use. Whichever system is used, many of the STR regions under test are the same. These DNA-profiling systems are based around multiplex reactions, whereby many STR regions will be under test at the same time. Capillary electrophoresis works by electrokinetically (movement through the application of an electric field) injecting the DNA fragments into a thin glass tube (the capillary) filled with polymer. The DNA is pulled through the tube by the application of an electric field, separating the fragments such that the smaller fragments travel faster through the capillary. The fragments are then detected using fluorescent dyes that were attached to the primers used in PCR. This allows multiple fragments to be amplified and run simultaneously, something known as multiplexing. Sizes are assigned using labeled DNA size standards that are added to each sample, and the number of repeats are determined by comparing the size to an allelic ladder, a sample that contains all of the common possible repeat sizes. Although this method is expensive, larger capacity machines with higher throughput are being used to lower the cost/sample and reduce backlogs that exist in many government crime facilities. Gel electrophoresis acts using similar principles as CE, but instead of using a capillary, a large polyacrylamide gel is used to separate the DNA fragments. An electric field is applied, as in CE, but instead of running all of the samples by a detector, the smallest fragments are run close to the bottom of the gel and the entire gel is scanned into a computer. This produces an image showing all of the bands corresponding to different repeat sizes and the allelic ladder. This approach does not require the use of size standards, since the allelic ladder is run alongside the samples and serves this purpose. Visualization can either be through the use of fluorescently tagged dyes in the primers or by silver staining the gel prior to scanning. Although it is cost-effective and can be rather high throughput, silver staining kits for STRs are being discontinued. In addition, many labs are phasing out gels in favor of CE as the cost of machines becomes more manageable. The true power of STR analysis is in its statistical power of discrimination. In the US, there are 13 core loci (DNA locations) that are currently used for discrimination in CODIS. Because these loci are [[independent assortment|independently assorted]] (having a certain number of repeats at one locus doesn't 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 (1 with 18 zeros after it) or more. ===AmpFLP=== {{main|Amplified fragment length polymorphism}} 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 locus 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. ===Y-chromosome analysis=== 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 and/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. It turns out that he did. ===Mitochondrial analysis=== {{main|Mitochondrial DNA}} 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, 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 sister's son. A difference of two or more nucleotides is generally 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 unclear identities, such as those of missing persons 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]]. mtDNA can be obtained from such material as hair shafts and old bones/teeth. ==National DNA databases== The [[United States]] maintains the largest [[DNA database]] in the world: [[CODIS|The Combined DNA Index System]], with over 5 million records as of [[2007]]<ref>[http://www.fbi.gov/hq/lab/codis/national.htm CODIS - National DNA Index System<!-- Bot generated title -->]</ref>. The [[United Kingdom]] maintains the [[UK National DNA Database|National DNA Database]] (NDNAD), which is of similar size. The size of this database, and its rate of growth, is 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.<ref>[http://www.wikicrimeline.co.uk/index.php?title=Identification_by_body_samples_and_impressions#Section_82:_Restrictions_on_use_and_destruction_of_fingerprints_and_samples Restrictions on use and destruction of fingerprints and samples]</ref> The [[USA PATRIOT Act|U.S. Patriot Act]] of the United States provides a means for the U.S. government to get DNA samples from other countries if they{{Clarifyme|date=April 2008}} <!--who? employees? you can't get a DNA sample for a division or a head office-->are either a division of, or head office of, a company operating in the U.S. Under the act, the American offices of the company can't divulge to their subsidiaries/offices in other countries the reasons that these DNA samples are sought or by whom.{{Fact|date=April 2008}} ==Considerations when evaluating DNA evidence== 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 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. 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 guilt and is known as the [[prosecutor's fallacy]]. When using RFLP, the theoretical risk of a coincidental match is 1 in 100 billion (100,000,000,000). However, 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 [http://www.guardian.co.uk/crime/article/0,2763,640157,00.html]. 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 [http://www.nap.edu/openbook/0309053951/html/35.html]. Today, RFLP has become widely disused due to the advent of more discriminating, sensitive and easier technologies. STRs do not suffer from such subjectivity and provide similar power of discrimination (1 in 10^13 for unrelated individuals if using a full SGM+ profile) It should be noted that 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 (one thousand million) is considered statistically supportable (Since 1998 the DNA profiling system supported by The National DNA Database in the UK is the SGM+ DNA profiling system which includes 10 STR regions and a sex indicating test. 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. ==Fake DNA evidence== The value of DNA evidence has to be seen in light of recent cases where criminals planted fake DNA samples at crime scenes. In one case, a criminal even planted fake DNA evidence in his own body: Dr. [[John Schneeberger]] of Canada raped one of his sedated patients in 1992 and left semen on her underwear. Police drew 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 [[anticoagulant]]s. ==DNA Evidence as Evidence in Criminal Trials== {{EvidenceLaw}} ===England and Wales=== 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.<ref>{{cite court |litigants=R v. Loveridge |reporter=EWCA Crim |opinion=734 |date=2001 |url= }}</ref>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 'likelihood ratio' (the probability that a person with matching DNA committed the crime). In {{cite court |litigants=R v. Doheny |reporter=EWCA Crim |opinion=728 |date=1996 |url=http://www.bailii.org/cgi-bin/markup.cgi?doc=/ew/cases/EWCA/Crim/1996/728.html&query=doheny&method=boolean }} Phillips LJ gave this example of a summing up, which should be carefully tailored to the particular facts in each case: <blockquote>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.</blockquote> 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"<ref>{{cite court |litigants=R v. Adams |reporter=EWCA Crim |opinion=2474 |date=1997 |url=http://www.bailii.org/cgi-bin/markup.cgi?doc=/ew/cases/EWCA/Crim/1997/2474.html&query=doheny&method=boolean }}</ref>. =====Presentation and evaluation of evidence of partial or incomplete DNA profiles===== R v Bates (2006) EWCA Crim 1395 Moore-Bick LJ said: :“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 exists which would assist the accused and perhaps even exculpate him altogether, 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”. <ref>[http://www.wikicrimeline.co.uk/index.php?title=DNA_profiling#Presentation_and_evaluation_of_evidence_of_partial_or_incomplete_DNA_profiles WikiCrimeLine DNA profiling]</ref> ===Familial searching=== Familial searching is the use of family members' DNA to identify a closely related suspect in jurisdictions where large DNA databases exist, but no exact match has been found. The first successful use of the practice was in a UK case where a man was convicted of [[manslaughter]] when he threw a brick stained with his own blood into a moving car. Police could not get an exact match to the UK's DNA databased because the man had no criminal convictions, but police implicated him using a close relative's DNA.<ref>{{cite news |first=Shaoni |last=Bhattacharya |title=Killer convicted thanks to relative's DNA |url=http://www.newscientist.com/article/dn4908-killer-convicted-thanks-to-relatives-dna.html |publisher=''[[New Scientist]]'' |date=[[20 April]] [[2004]] |accessdate=2008-05-06 }}</ref> The practice, which is slated for expansion in the American state of California, has proved controversial because of civil liberties concerns regarding the disproportionate representation of blacks in DNA databases.<ref>{{cite news |title=Genetics and privacy: Hands off, maybe |url=http://www.economist.com/world/na/displaystory.cfm?story_id=11293939 |publisher=''[[The Economist]]'' |date=[[1 May]] [[2008]] |accessdate=2008-05-06 }}</ref> ==Cases== In the 1950s, [[Anna Anderson]] claimed that she was [[Grand Duchess Anastasia Nikolaevna of Russia]]; in the 1980s after her death, samples of her tissue that had been stored at a Charlottesville, Virginia hospital following a medical procedure were tested using DNA fingerprinting and showed that she bore no relation to the [[Romanovs]]. <ref> Identification of the remains of the Romanov family by DNA analysis by Peter Gill, Central Research and Support Establishment, Forensic Science Service, Aldermaston, Reading, Berkshire, RG7 4PN, UK, Pavel L. Ivanov, Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, 117984, Moscow, Russia, Colin Kimpton, Romelle Piercy, Nicola Benson, Gillian Tully, Ian Evett, Kevin Sullivan, Forensic Science Service, Priory House, Gooch Street North, Birmingham B5 6QQ, UK, Erika Hagelberg, University of Cambridge, Department of Biological Anthropology, Downing Street, Cambridge CB2 3DZ, UK - http://www.nature.com/ng/journal/v6/n2/abs/ng0294-130.html </ref> In 1987, [[United Kingdom|British]] baker [[Colin Pitchfork]] was the first criminal caught using DNA fingerprinting in [[Leicester]], the city where it was first discovered. 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 [[6 November]] [[1987]] and sentenced to 22 years in prison. [http://www.txtwriter.com/Backgrounders/Genetech/GEpage14.html] [http://www.pbs.org/wgbh/pages/frontline/shows/case/revolution/databases.html] In 1988, [[Timothy 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 southside of Richmond, Virginia. He was later charged with rape and 1st 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 [[United States|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 [[Canada|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 [[Nazism|Nazi]] doctor [[Josef Mengele]] was buried in [[Brazil]] under the name Wolfgang Gerhard. In 1993, [[Kirk Bloodsworth]] was the first person to have been convicted of [[murder]] and [[capital punishment|sentenced to death]], whose conviction was overturned using DNA evidence. The science was made famous in the [[United States]] in 1994 when prosecutors heavily relied on &mdash; and through expert witnesses exhaustively presented and explained &mdash; DNA evidence allegedly linking [[O.J. Simpson]] to a double murder. The case also brought to light the laboratory difficulties and handling procedure mishaps which can cause such evidence to be significantly doubted. In 1994, RCMP detectives successfully tested hairs from a cat known as [[Snowball the Cat|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 DNA to identify a criminal. In 1998, Dr. [[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 [[HIV|human immunodeficiency virus]] (HIV) he had been accused of injecting in his girlfriend and viral DNA from one of his patients with full-blown 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 7 hours in connection with a burglary due to an inaccurrate DNA match. His DNA had been retained on file after an unrelated domestic incident some time previously. <ref> {{cite web |url=http://www.guardian.co.uk/comment/story/0,,1933724,00.html |title = Suspect Nation |publisher = The Guardian |date = [[2006-10-08]]}} </ref> In 2001, Wayne Butler was convicted for the murder of [[Murder of Celia Douty|Celia Douty]]. It was the first murder in [[Australia]] to be solved using DNA profiling.<ref name="telegraphuk">{{cite web|url=http://www.telegraph.co.uk/news/worldnews/australiaandthepacific/1322624/18-years-on%2C-man-is-jailed-for-murder-of-Briton-in-%27paradise%27.html|title=18 years on, man is jailed for murder of Briton in 'paradise'|last=Dutter|first=Barbie|date=2001-06-19|publisher=The Telegraph|accessdate=2008-06-17}}</ref><ref name="tv">{{cite web|url=http://www.abc.net.au/7.30/content/2004/s1195029.htm|title=DNA evidence may not be infallible: experts|last=McCutcheon|first=Peter|date=2004-09-08|publisher=Australian Broadcasting Corporation|accessdate=2008-06-17}}</ref> 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. Some time later, 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.[http://news.bbc.co.uk/1/hi/england/2766289.stm] 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 [[Short tandem repeat|STR]] techniques, resulting in a match with his nephew.[http://lifeloom.com/I2Sekar.htm] 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 June 2003, because of new DNA evidence, Dennis Halstead, John Kogut and John Restivo won a re-trial on their murder conviction. The three men had already served eighteen years of their thirty-plus-year sentences. The trial of [[Robert Pickton]] is notable in that DNA evidence is being used primarily to identify the ''victims'', and in many cases to prove their existence. 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 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.<ref>"[http://www.usatoday.com/tech/news/2004-05-05-1914-dna_x.htm DNA clears man of 1914 kidnapping conviction]," ''USA Today'', (May 5, 2004), by Allen G. Breed, Associated Press.</ref> 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. ==See also== * [[National DNA database]] * [[restriction fragment length polymorphism]] (RFLP) * [[Parental testing]] * [[genealogical DNA test]] * [[short tandem repeat]] (STR) * [[capillary electrophoresis]] (CE) * [[Gene mapping]] * ''[[Harvey v. Horan]]'' * [[ribotyping]] ==References== {{reflist|2}} ==External links== *[http://www.thenakedscientists.com/html/columnists/dalyacolumn8.htm How to make a DNA (genetic) Fingerprint and applications of DNA Fingerprinting] *[http://www.pbs.org/wgbh/nova/sheppard/analyze.html Create a DNA Fingerprint] *[http://www.nature.com/ng/journal/v36/n11s/abs/ng1594.html Forensic genetics and ethical, legal and social implications beyond the clinic] *[http://insilico.ehu.es In silico simulation of Molecular Biology Techniques] - A place to learn typing techniques by simulating them [[Category:Applied genetics]] [[Category:Biometrics]] [[Category:DNA]] [[Category:Molecular biology]] [[Category:Personal identification]] [[Category:Forensics]] [[cs:Genetická daktyloskopie]] [[de:Genetischer Fingerabdruck]] [[es:Huella genética]] [[fr:Empreinte génétique]] [[ko:법의유전학]] [[it:Impronta genetica]] [[nl:Genetische vingerafdruk]] [[ja:DNA型鑑定]] [[no:Genetisk fingeravtrykk]] [[sl:Iskanje prstnih odtisov DNA]] [[sr:ДНК анализа]] [[fi:DNA-testi]] [[zh:遺傳指紋分析]]