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In the early 1980s, British scientist Alec Jeffreys—who later received a knighthood for his work—invented the technique which he called DNA fingerprinting. His research group was working on finding markers which could be used to detect genetic diseases, but a serendipitous discovery prompted Jeffreys to develop a technique that has since been used in thousands of criminal investigations.
What exactly is DNA fingerprinting? Like fingerprints themselves, everyone’s DNA profile is unique, and this provides investigators with a highly sophisticated tool for using crime scene evidence to convict criminals.
These two articles provide some information on how DNA samples are taken, and how they are processed to provide meaningful information for use by criminal investigators.
DNA samples are typically pretty small, and they don't always contain a large amount of usable DNA. But that doesn't have to be a barrier to finding who left their DNA at a crime scene. In these situations, a technique called the polymerase chain reaction (PCR) can be used to amplify the DNA sample. In the PCR, the sample is used as the template for building more copies of the DNA itself, via a series of enzyme reactions. In a relatively short amount of time, a small sample can be used to generate a much larger amount of the same DNA sequence. This technique is particularly useful in old cases where physical evidence was collected, but where the DNA has been subject to age-related degradation.
Although the best-known use of DNA fingerprinting is in forensics, this technology does in fact have many other applications. In fact, the first use of the technique was in an immigration case, rather than a criminal investigation.
The first use of DNA fingerprinting in a trial established the innocence of man who had been accused of raping and murdering two schoolgirls. The biological evidence was then later used to locate and convict the real killer. Following this landmark case many countries decided to adopt the technology.
Three US cases highlight the importance of DNA evidence in a variety of situations. In the case of Tommie Lee Andrews, DNA evidence was used to convict a serial rapist. The conviction of death row inmate Kirk Bloodsworth was overturned on the basis of DNA evidence, and the evidence in the OJ Simpson case is a prime example of how incorrectly collected and handled DNA samples can muddy the waters in a criminal case.
Even decades-old cases can be solved by testing samples of DNA left at a crime scene. In some situations old DNA samples can be used to apprehend an offender with the use of a profiling technique called familial searching.
Mitochondrial DNA profiling is particularly interesting because of the way this type of DNA is passed down through the generations. It’s passed down from mother to child, rather than being a mix of the DNA of both parents, and genetic testing with this method has advantages and drawbacks because of this.
One of America’s most famous outlaws, Jesse James, is reputedly buried in Kearney, Missouri. In 1995 the body was exhumed for genetic testing, and a DNA sample was extracted and compared with samples from descendants of Jesse James. What did the tests reveal?
The urban legend of the surviving member of the Romanov royal family has persisted since the Russian royals were shot by Bolsheviks in July 1918. More than one woman has claimed to be the royal princess Anastasia, but DNA evidence has once and for all proved that no members of the royal family survived the shooting.
Is DNA profiling the be-all end-all, or simply one tool of many that investigators have available? One team of scientists has demonstrated that it’s possible to fake DNA evidence, but this does not necessarily mean that this type of evidence is no longer useful.
The use of DNA profiling has become an important part of the criminal justice system, but concerns are often raised about social, ethical, and legal issues that arise as a result of this technology. Read this article to learn more about arguments for and against the use of DNA in forensics.
- This is a compilation of articles contained on the Bright Hub site. References and resources used by the authors to create each piece of content within the compilation can be found on the individual articles themselves.