DNA Evidence

DNA is unique in each individual. Given that each person is genetically unique, material and fluids found at crime scenes can be used to identify the perpetrator. DNA evidence usually refers to the use of this technology at criminal trials.

On March 2, 2009, the Supreme Court heard arguments in a case brought by a federal inmate in Alaska who wants access to DNA evidence from his court case to help overturn his rape conviction. Alaska is one of six states that do not give convicted felons such access.New York Times: The Right to DNA Evidence (March 1, 2009)

DNA is collected at a crime scene by carefully extracting samples of hair, fingernails, teeth, blood, or other bodily fluids that have been left behind. The DNA is then extracted from the tissue sample and analyzed. If the suspect is known, the sample of DNA would be compared to the sample of the suspect. If the suspect is unknown, investigators will use an FBI computer program called CODIS to match the sample DNA with another in the database.

DNA evidence can prove that a suspect was involved in a crime. On the other hand, there have been many instances of DNA evidence leading to the overturning of a conviction when the DNA does not link the accused to a crime. In several criminal cases DNA evidence has proven the innocence of those wrongfully accused.

The case in court is from William Osborne, a man convicted in 1993 on the basis of DNA evidence for the rape and physical assault of a Anchorage prostitute. The test used in 1993 is known as the D-Q test, which cannot identify specific persons. Since Osborne's conviction, a new more sensitive DNA test has been created, the STR test. Osborne argues the STR test would prove his innocence. The Alaska state courts rejected that argument, and Osborne's attorneys appealed.New York Times: The Right to DNA Evidence (March 1, 2009)

• The Innocence Project