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DNA profiling is a forensic technique in criminal investigations, comparing criminal suspects' profiles to DNA evidence so as to assess the likelihood of their involvement in the crime.[1] It is also used in parentage testing,[2] to establish immigration eligibility,[3] and in genealogical and medical research. DNA profiling has also been used in the study of animal and plant populations in the fields of zoology, botany, and agriculture.[4]



Starting in the 1980s scientific advances allowed for the use of DNA as a mechanism for the identification of an individual. The first patent covering the modern process of DNA profiling was filed by Dr. Jeffrey Glassberg[5] in 1983, based upon work he had done while at Rockefeller University in 1981. Glassberg, along with two medical doctors, founded Lifecodes Corporation[6][7] to bring this invention to market. The Glassberg patent was issued in Belgium BE899027A1,[8] Canada FR2541774A1,[9] Germany DE3407196 A1,[10] Great Britain GB8405107D0,[11] Japan JPS59199000A,[12] United States as US5593832A.[13][14] In the United Kingdom, Geneticist Sir Alec Jeffreys[15][16][17][18] independently developed a DNA profiling process in beginning in late 1984[19] while working in the Department of Genetics at the University of Leicester.[20]

The process, developed by Jeffreys in conjunction with Peter Gill and Dave Werrett of the Forensic Science Service (FSS), was first used forensically in the solving of the murder of two teenagers who had been raped and murdered in Narborough, Leicestershire in 1983 and 1986. In the murder inquiry, led by Detective David Baker, the DNA contained within blood samples obtained voluntarily from around 5,000 local men who willingly assisted Leicestershire Constabulary with the investigation, resulted in the exoneration of Richard Buckland, an initial suspect who had confessed to one of the crimes, and the subsequent conviction of Colin Pitchfork on January 2, 1988. Pitchfork, a local bakery employee, had coerced his coworker Ian Kelly to stand in for him when providing a blood sample—Kelly then used a forged passport to impersonate Pitchfork. Another coworker reported the deception to the police. Pitchfork was arrested, and his blood was sent to Jeffrey's lab for processing and profile development. Pitchfork's profile matched that of DNA left by the murderer which confirmed Pitchfork's presence at both crime scenes; he pleaded guilty to both murders.[21]

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.[22] DNA profiling uses repetitive sequences that are highly variable,[22] called variable number tandem repeats (VNTRs), in particular short tandem repeats (STRs), also known as microsatellites, and minisatellites. VNTR loci are similar between closely related individuals, but are so variable that unrelated individuals are unlikely to have the same VNTRs.

In India DNA fingerprinting was started by Dr. VK Kashyap and Dr. Lalji Singh. Singh was an Indian scientist who worked in the field of DNA fingerprinting technology in India, where he was popularly known as the "Father of Indian DNA fingerprinting".[23] In 2004, he received the Padma Shri in recognition of his contribution to Indian science and technology.[24]

Profiling processesEdit

Variations of VNTR allele lengths in 6 individuals.
Alec Jeffreys, a pioneer of DNA profiling.

The process, developed by Glassberg and independently by Jeffreys, begins with a sample of an individual's DNA (typically called a "reference sample"). Reference samples are usually collected through a buccal swab. When this is unavailable (for example, when a court order is needed but unobtainable) other methods may be needed to collect a sample of blood, saliva, semen, vaginal lubrication, or other fluid or tissue from personal use items (for example, a toothbrush, razor) or from stored samples (for example, banked sperm or biopsy tissue). Samples obtained from blood relatives can indicate an individual's profile, as could previous profiled human remains. A reference sample is then analyzed to create the individual's DNA profile using one of the techniques discussed below. The DNA profile is then compared against another sample to determine whether there is a genetic match.

DNA ExtractionEdit

When a sample such as blood or saliva is obtained, the DNA is only a small part of what is present in the sample. Before the DNA can be analyzed, it must be extracted from the cells and purified. There are many ways this can be accomplished, but all methods follow the same basic procedure. The cell and nuclear membranes need to be broken up to allow the DNA to be free in solution. Once the DNA is free, it can be separated from all other cellular components. After the DNA has been separated in solution, the remaining cellular debris can then be removed from the solution and discarded, leaving only DNA.[25] The most common methods of DNA extraction include organic extraction (also called phenol chloroform extraction), Chelex extraction, and solid phase extraction. Differential extraction is a modified version of extraction in which DNA from two different types of cells can be separated from each other before being purified from the solution. Each method of extraction works well in the laboratory, but analysts typically selects their preferred method based on factors such as the cost, the time involved, the quantity of DNA yielded, and the quality of DNA yielded.[26] After the DNA is extracted from the sample, it can be analyzed, whether it be RFLP analysis or quantification and PCR analysis.

RFLP analysisEdit

The first methods for finding out genetics used for DNA profiling involved RFLP analysis. DNA is collected from cells and cut into small pieces using a restriction enzyme (a restriction digest). This generates 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.


The Southern blot technique requires large amounts of non-degraded 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.

Polymerase chain reaction (PCR) analysisEdit

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, 1985) 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.



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.

STR analysisEdit



From country to country, different STR-based DNA-profiling systems are in use. In North America, systems that amplify the CODIS 20[28] 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.[29] 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.





DNA family relationship analysisEdit

1: A cell sample is taken- usually a cheek swab or blood test 2: DNA is extracted from sample 3: Cleavage of DNA by restriction enzyme- the DNA is broken into small fragments 4: Small fragments are amplified by the polymerase chain reaction- results in many more fragments 5: DNA fragments are separated by electrophoresis 6: The fragments are transferred to an agar plate 7: On the agar plate specific DNA fragments are bound to a radioactive DNA probe 8: The agar plate is washed free of excess probe 9: An x-ray film is used to detect a radioactive pattern 10: The DNA is compared to other DNA samples




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.

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.



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

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.




Y-chromosome analysisEdit


Mitochondrial analysisEdit


mtDNA can be obtained from such material as hair shafts and old bones/teeth.[32] Control mechanism based on interaction point with data. This can be determined by tooled placement in sample.[citation needed]

Issues with forensic DNA samplesEdit

When people think of DNA analysis they often think about shows like NCIS or CSI, which portray DNA samples coming into a lab and then instantly analyzed, followed by pulling up a picture of the suspect within minutes⁠ ⁠—⁠ ⁠the reality, however, is quite different, and perfect DNA samples are often not collected from the scene of a crime. Homicide victims are frequently left exposed to harsh conditions before they are found and objects used to commit crimes have often been handled by more than one person. The two most prevalent issues that forensic scientists encounter when analyzing DNA samples are degraded samples and DNA mixtures.

Degraded DNAEdit

In the real world DNA labs often have to deal with DNA samples that are less than ideal. DNA samples taken from crime scenes are often degraded, which means that the DNA has started to break down into smaller fragments DNA fragmentation. Victims of homicides might not be discovered right away, and in the case of a mass casualty event it could be hard to get DNA samples before the DNA has been exposed to degradation elements.

Degradation or fragmentation of DNA at crime scenes can occur because of a number of reasons, with environmental exposure often being the most common cause. Biological samples that have been exposed to the environment can get degraded by water and enzymes called nucleases Nuclease. Nucleases essentially ‘chew’ up the DNA into fragments over time and are found everywhere in nature.

Before modern PCR methods existed it was almost impossible to analyze degraded DNA samples. Methods like restriction fragment length polymorphism or RFLP Restriction fragment length polymorphism, which was the first technique used for DNA analysis in forensic science, required high molecular weight DNA in the sample in order to get reliable data. High molecular weight DNA however is something that is lacking in degraded samples, as the DNA is too fragmented to accurately carry out RFLP. It wasn't until modern day PCR techniques were invented that analysis of degraded DNA samples were able to be carried out Polymerase chain reaction. Multiplex PCR in particular made it possible to isolate and amplify the small fragments of DNA still left in degraded samples. When multiplex PCR methods are compared to the older methods like RFLP a vast difference can be seen. Multiplex PCR can theoretically amplify less than 1 ng of DNA, while RFLP had to have a least 100 ng of DNA in order to carry out an analysis.[33]

In terms of a forensic approach to a degraded DNA sample, STR loci STR analysis are often amplified using PCR-based methods. Though STR loci are amplified with greater probability of success with degraded DNA, there is still the possibility that larger STR loci will fail to amplify, and therefore, would likely yield a partial profile, which results in reduced statistical weight of association in the event of a match.

MiniSTR AnalysisEdit

In instances where DNA samples are degraded, like in the case of intense fires or if all that remains are bone fragments, standard STR testing on these samples can be inadequate. When standard STR testing is done on highly degraded samples the larger STR loci often drop out, and only partial DNA profiles are obtained. While partial DNA profiles can be a powerful tool, the random match probabilities will be larger than if a full profile was obtained. One method that has been developed in order to analyse degraded DNA samples is to use miniSTR technology. In this new approach, primers are specially designed to bind closer to the STR region.[34] In normal STR testing the primers will bind to longer sequences that contain the STR region within the segment. MiniSTR analysis however will just target the STR location, and this results in a DNA product that is much smaller.[34]

By placing the primers closer to the actual STR regions, there is a higher chance that successful amplification of this region will occur. Successful amplification of these STR regions can now occur and more complete DNA profiles can be obtained. The success that smaller PCR products produce a higher success rate with highly degraded samples was first reported in 1995, when miniSTR technology was used to identify victims of the Waco fire.[35] In this case the fire at destroyed the DNA samples so badly that normal STR testing did not result in a positive ID on some of the victims.

DNA MixturesEdit

Mixtures are another common issue that forensic scientists face when they are analyzing unknown or questionable DNA samples. A mixture is defined as a DNA sample that contains two or more individual contributors.[36] This can often occur when a DNA sample is swabbed from an item that is handled by more than one person or when a sample contains both the victim and assailants' DNA. The presence of more than one individual in a DNA sample can make it challenging to detect individual profiles, and interpretation of mixtures should only be done by highly trained individuals. Mixtures that contain two or three individuals can be interpreted, though it will be difficult. Mixtures that contain four or more individuals are much too convoluted to get individual profiles. One common scenario in which a mixture is often obtained is in the case of sexual assault. A sample may be collected that contains material from the victim, the victim's consensual sexual partners, and the perpetrator(s).[37]

As detection methods in DNA profiling advance, forensic scientists are seeing more DNA samples that contain mixtures, as even the smallest contributor is now able to be detected by modern tests. The ease in which forensic scientists have in interpenetrating DNA mixtures largely depends on the ratio of DNA present from each individual, the genotype combinations, and total amount of DNA amplified.[38] The DNA ratio is often the most important aspect to look at in determining whether a mixture can be interpreted. For example, in the case where a DNA sample had two contributors, it would be easy to interpret individual profiles if the ratio of DNA contributed by one person was much higher than the second person. When a sample has three or more contributors, it becomes extremely difficult to determine individual profiles. Fortunately, advancements in probabilistic genotyping could make this sort of determination possible in the future. Probabilistic genotyping uses complex computer software to run through thousands of mathematical computations in order to produce statistical likelihoods of individual genotypes found in a mixture.[39] Probabilistic genotyping software that are often used in labs today include STRmix and TrueAllele.

DNA databasesEdit

An early application of a DNA database was the compilation of a Mitochondrial DNA Concordance,[40] prepared by Kevin W. P. Miller and John L. Dawson at the University of Cambridge from 1996 to 1998[41] 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.[42] 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.[43] 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) offenses. Public discourse around the introduction of advanced forensic techniques (such as genetic genealogy using public genealogy databases and DNA phenotyping approaches) has been limited, disjointed, unfocused, and raises issues of privacy and consent that may warrant the establishment of additional legal protections.[44]

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.[45]

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 database, 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.[46]

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.[47] The DNA of the perpetrator, collected from victims of rape, can be stored for years until a match is found. In 2014, to address this problem, Congress extended a bill that helps states deal with "a backlog" of evidence.[48]

Considerations when evaluating DNA evidenceEdit

As DNA profiling became a key piece of evidence in the court, defense lawyers based their arguments on statistical reasoning. For example: 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.



Evidence of genetic relationshipEdit

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.[51] This happens when two eggs are fertilized at the same time and fuse together to create one individual instead of twins.

Fake DNA evidenceEdit


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.[52] 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.[53]

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.

DNA evidence in criminal trialsEdit

Familial DNA searchingEdit

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.[54][55] 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.[56] 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.

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[57] 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.[58] 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.[59] California was the first state to implement a policy for familial searching under then Attorney General, now Governor, Jerry Brown.[60] 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.[61] 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.[62] 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.[63] In March 2011 Virginia Governor Bob McDonnell announced that Virginia would begin using familial DNA searches.[64] Other states are expected to follow.


Critics of familial DNA database searches argue that the technique is an invasion of an individual's 4th Amendment rights.[66] 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.[47] Some scholars have pointed out that the privacy concerns surrounding familial searching are similar in some respects to other police search techniques,[67] and most have concluded that the practice is constitutional.[68] 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.[69] 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.


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.[70] 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.

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 Bossetti who was arrested and accused of the murder of the 13-year-old girl. In the summer of 2016 Bossetti was found guilty and sentenced to life by the Corte d'assise of Bergamo.

Partial matchesEdit

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.[71] 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,[72] 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.[73] 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).

Surreptitious DNA collectingEdit

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.[74]

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."[75]

The United States Supreme Court ruled in Maryland v. King (2013) that DNA sampling of prisoners arrested for serious crimes is constitutional.[76][77][78]

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.[79]

England and WalesEdit

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.[80] 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[81] Phillips LJ gave this example of a summing up, which should be carefully tailored to the particular facts in each case:



Presentation and evaluation of evidence of partial or incomplete DNA profilesEdit

In R v Bates,[83] Moore-Bick LJ said:


DNA testing in the United StatesEdit


There are state laws on DNA profiling in all 50 states of the United States.[85] Detailed information on database laws in each state can be found at the National Conference of State Legislatures website.[86]

Development of artificial DNAEdit



The New York Times quoted the lead author, Daniel Frumkin, saying, "You can just engineer a crime scene ... any biology undergraduate could perform this".[87] Frumkin perfected a test that can differentiate real DNA samples from fake ones. His test detects epigenetic modifications, in particular, DNA methylation.[88] 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.[87]



  • 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.[90] 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.[91]
  • 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.
  • 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, 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.[99] His case is often cited by opponents of the death penalty.
  • 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.[101] In view of this the Florida state governor ordered that in future any death row inmate claiming innocence should have DNA testing.[99]
  • 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.[103][104]
  • 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.[109] 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, their convictions were struck down and they were released.[110] The three men had already served eighteen years of their thirty-plus-year sentences.
  • 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.[116]
  • 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.[117][118]
  • 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.[119][120]
  • In 2018 the Buckskin girl (a body found in 1981 in Ohio) was identified as Marcia King from Arkansas using DNA genealogical techniques[121]
  • In 2018 Joseph James DeAngelo was arrested as the main suspect for the Golden State Killer using DNA and genealogy techniques.[122]
  • In 2018 William Earl Talbott II was arrested as a suspect for the 1987 murder of Jay Cook and Tanya Van Cuylenborg with the assistance of DNA genealogical techniques. The same genetic genealogist that helped in this case also helped police with 18 other arrests in 2018.[123]

DNA evidence as evidence to prove rights of succession to British titlesEdit

DNA testing is used to establish the right of succession to British titles.[124]


See alsoEdit


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Further readingEdit

External linksEdit