What is Forensic DNA Testing?

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  • Written By: Jessica Ellis
  • Edited By: Bronwyn Harris
  • Images By: Gorilla, Wavebreakmediamicro, Ferrerilavarialiotti, Irri Photos
  • Last Modified Date: 17 January 2020
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Forensic DNA testing uses advanced testing techniques to aid the legal system in a variety of cases. Typically, this type of testing is used in questions of identity, such as placing a criminal at a crime scene or establishing paternity. Forensic DNA testing uses samples of bodily fluids, skin or even hair to correctly determine the identity of the person tested by their genetic code.

Human beings each have a distinct code embedded in their DNA, much like a unique credit card number or home address. Although relatives may have similar genetic codes, there is little evidence suggesting that any two people could have an identical code. By taking a reference sample such as a mouth swab from a suspect and comparing it to physical evidence found at a crime scene, forensic scientists can determine if the DNA from the two samples is a match.

There are several different methods used in forensic DNA testing, depending on the type of samples acquired and the needs of the test. In paternity testing, forensic scientists may look at the composition of the Y-chromosome, which is passed on genetically from the father to the child. Other methods involve comparing specific repeating patterns found in DNA, or examining the nucleus in the cells examined.


Forensic DNA testing is a relatively new form of establishing identity, and new forms of testing are still being discovered. The technology to do DNA testing has only been available to the legal system since the late 1980s, after a landmark paper about possibilities of the field was published in 1985 by Sir Alec Jeffries. Although the technique is still in its infancy, it has proved its usefulness to the court system by more accurately establishing physical evidence.

Forensic DNA testing has also lead to the redemption of many innocent people that were found guilty without sufficient physical evidence. In the United States, nearly 200 people have been exonerated by the testing or retesting of DNA evidence through methods not available at the time of their trial. Critics of the death penalty system have used these cases to reignite debate about capital punishment, pointing to the likelihood that the state has executed innocent people.

Using forensic DNA testing is hardly universally popular, however, and critics raise a number of important objections. Testing methods are difficult and delicate, and results can be contaminated or destroyed in a variety of ways. The wary also suggest that it would be possible to plant DNA evidence at a crime scene to implicate a particular person.

Other critics also worry about the creation of DNA databases, such as those in the United States, United Kingdom and New Zealand. While these databases are meant to record genetic evidence of criminals to connect them to possible future crimes, critics worry that this may compromise personal freedom and constitute an illegal search. These critiques clearly show that while forensic DNA testing is a marvelous tool of the legal system, it is far from infallible and requires further research and continued development of testing techniques.



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