DNA Evidence Basics

DNA collection and analysis gives the criminal justice field a powerful tool for convicting the guilty and exonerating the innocent. These pages provide​ 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. After extracting DNA from bone, hair, blood or other body tissue or product, scientists record an individual’s variations at these bases to generate their ‘DNA profile.’

In criminal cases, this generally involves obtaining samples from crime-scene evidence and a suspect, extracting the DNA, and analyzing it to characterize the variations at a set of specific variable 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.

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Date Modified: January 25, 2019