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. It is also used in parentage testing, to establish immigration eligibility, 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.
Background
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
in 1983, based upon work he had done while at Rockefeller University in
1981. Glassberg, along with two medical doctors, founded Lifecodes
Corporation to bring this invention to market. The Glassberg patent was issued in Belgium BE899027A1, Canada FR2541774A1, Germany DE3407196 A1, Great Britain GB8405107D0, Japan JPS59199000A, United States as US5593832A. In the United Kingdom, Geneticist Sir Alec Jeffreys independently developed a DNA profiling process in beginning in late 1984 while working in the Department of Genetics at the University of Leicester.
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.
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. DNA profiling uses repetitive sequences that are highly variable, 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.
DNA profiling processes
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 Extraction
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. 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. After the DNA is extracted from the sample, it can be analyzed, whether it be RFLP analysis or quantification and PCR analysis.
RFLP analysis
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 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.
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) analysis
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.
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.
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.
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 analysis
The system of DNA profiling used today is based on polymerase chain reaction (PCR) and uses simple sequences
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.
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.
From country to country, different STR-based DNA-profiling systems are in use. In North America, systems that amplify the CODIS 20 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.
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.
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. Moreover, since there are about 12 million monozygotic twins on Earth, the theoretical probability is not accurate.
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.
AFLP
Another technique, AFLP, 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.
DNA family relationship analysis
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
Using PCR
technology, DNA analysis is widely applied to determine genetic family
relationships such as paternity, maternity, siblingship and other
kinships.
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.
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.
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.
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.
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:
| 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.
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.
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.
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.
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 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.
Mitochondrial analysis
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.
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.
Issues with forensic DNA samples
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 DNA
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.
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 Analysis
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.
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.
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.
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 Mixtures
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.
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).
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.
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. Probabilistic genotyping software that are often used in labs today include STRmix and TrueAllele.
DNA databases
An early application of a DNA database was the compilation of a Mitochondrial DNA Concordance, prepared by Kevin W. P. Miller and John L. Dawson at the University of Cambridge from 1996 to 1998 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. 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. 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.
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.
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.
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.
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.
Considerations when evaluating DNA evidence
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.
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.
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.
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. Today, RFLP has become widely disused due to the advent of more discriminating, sensitive and easier technologies.
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.
Evidence of genetic relationship
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. This happens when two eggs are fertilized at the same time and fuse together to create one individual instead of twins.
Fake DNA evidence
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.
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.
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.
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 trials
Familial DNA searching
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.
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. 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
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.
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. California was the first state to implement a policy for familial searching under then Attorney General, now Governor, Jerry Brown. 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.
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.
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. In March 2011 Virginia Governor Bob McDonnell announced that Virginia would begin using familial DNA searches. Other states are expected to follow.
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.
Critics of familial DNA database searches argue that the technique is an invasion of an individual's 4th Amendment rights.
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.
Some scholars have pointed out that the privacy concerns surrounding
familial searching are similar in some respects to other police search
techniques, and most have concluded that the practice is constitutional. 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.
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.
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.
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.
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
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.
Partial matches
Partial DNA matches are not searches themselves, but are the result of moderate stringency CODIS searches that produce a potential match that shares at least one allele at every locus.
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, 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.
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 collecting
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.
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."
The United States Supreme Court ruled in Maryland v. King (2013) that DNA sampling of prisoners arrested for serious crimes is constitutional.
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.
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.
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 Phillips LJ gave this example of a summing up, which should be carefully tailored to the particular facts in each case:
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.
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".
Presentation and evaluation of evidence of partial or incomplete DNA profiles
In R v Bates, 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 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.
DNA testing in the United States
CBP chemist reads a DNA profile to determine the origin of a commodity.
There are state laws on DNA profiling in all 50 states of the United States. Detailed information on database laws in each state can be found at the National Conference of State Legislatures website.
Development of artificial DNA
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.
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.
The New York Times
quoted the lead author, Daniel Frumkin, saying, "You can just engineer a
crime scene ... any biology undergraduate could perform this". Frumkin perfected a test that can differentiate real DNA samples from fake ones. His test detects epigenetic modifications, in particular, DNA methylation. 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.
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.
Cases
- 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. 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.
- 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.
- 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.
- 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.
- 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.
- 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. 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.
- 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. In view of this the Florida state governor ordered that in future any death row inmate claiming innocence should have DNA testing.
- 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.
- 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.
- 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". 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. 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.
- 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.
- 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. 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. 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- In 2018 the Buckskin girl (a body found in 1981 in Ohio) was identified as Marcia King from Arkansas using DNA genealogical techniques
- In 2018 Joseph James DeAngelo was arrested as the main suspect for the Golden State Killer using DNA and genealogy techniques.
- In 2018 William Earl Talbot, 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.
DNA evidence as evidence to prove rights of succession to British titles
DNA testing is used to establish the right of succession to British titles.
Cases:
