DNA Evidence Basics

DNA collection and analysis gives the criminal justice field a powerful tool for convicting the guilty and exonerating the innocent. About Forensic DNA provides general information on a wide range of topics.

Only one-tenth of a single percent of DNA (about 3 million bases) differs from one person to the next. Scientists can use these variable regions to generate a DNA profile of an individual, using samples from blood, bone, hair, and other body tissues and products.

In criminal cases, this generally involves obtaining samples from crime-scene evidence and a suspect, extracting the DNA, and analyzing it for the presence of a set of specific DNA regions (markers).

If the sample profiles don't match, the person did not contribute the DNA at the crime scene.

If the patterns match, the suspect may have contributed the evidence sample.

DNA from crime scenes also can be compared to profiles stored in a database.

Learn about:

Date Created: August 9, 2012