Q. What is the science behind forensic DNA testing?

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Deoxyribonucleic acid (DNA) is a molecule that contains genetic information. It is found in an organism’s cells and is the blueprint for that organism’s functions. DNA can be found in many biological materials because it is contained in every organism’s cells. In criminal cases, DNA is often found in biological evidence including blood, saliva, sweat, semen, hair, and skin. Each person’s genetic code is inherited and unique, so each DNA profile is distinct (except in identical twins).

Several tests have been developed that can find DNA profiles in biological evidence. For example, if an intruder cuts himself on a window while committing a burglary, forensic scientists would try to obtain a DNA profile from the blood on the window. That profile could then be compared to the profile of any suspect.

The current standard for forensic DNA testing is the Short Tandem Repeat (STR) test. This test includes elements of the Polymerase Chain Reaction (PCR) method, which allows for very small and degraded samples to be tested successfully. Mitochondrial DNA testing and Y-STR DNA testing have also been used more frequently in recent years.

Learn more about DNA and forensic testing here.

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