DNA as an Exoneration Tool

Law enforcement then searches a DNA database for potential matches. The search result matches with a person previously arrested in the same jurisdiction. Law enforcement obtains an arrest warrant and confronts the suspect. The suspect admits to the sexual assault of Stan's neighbor.

It seems like using DNA evidence has been around for a while, but it's a somewhat recent development. Courts used DNA evidence for the first time in a 1986 multiple-murder case out of Narborough, England. DNA evidence exonerated the original suspect, and law enforcement used forensic DNA to identify the real criminal.

Since then, courts have used forensic evidence to exonerate innocent people both before a trial and post-conviction. Advances in DNA technology have allowed courts to exonerate wrongfully convicted people on death row and correct miscarriages of justice.

This article describes how the criminal justice system uses DNA evidence in criminal cases. It describes post-conviction DNA testing and DNA exoneration cases. These cases typically involve forensic scientists conducting a DNA analysis of DNA samples in law enforcement's databases. Sometimes, the test results clear convicted felons of their convictions.

How Can DNA Exonerate Prisoners?

Law enforcement agencies often keep physical evidence from crimes for many years. Biological evidence, such as blood, hair, or skin, contains DNA. Forensic laboratories can test these samples and use them in one of three ways:

  • See if they match the person accused or convicted of a crime
  • Compare the DNA samples to a DNA database, such as CODIS. If the DNA matches a profile in a DNA database, law enforcement has a better chance of locating the person.
  • Compare DNA samples collected from different crime scenes

Post-conviction DNA testing involves testing DNA obtained from crime scenes using forensic science. The forensic laboratory will test the DNA samples against the convicted person's DNA profile. If it matches the convicted person's DNA profile, there is a good chance they convicted the right person. However, if it does not match, the jury may have convicted an innocent person.

How DNA Evidence Can Aid a Criminal Investigation

This section provides examples of how courts may use DNA evidence to aid in a criminal investigation or exonerate convicted people.


Suppose law enforcement arrests Stan for the alleged sexual assault of his neighbor in 2023. Law enforcement collected biological evidence from the crime scene. Stan denies the charges. Before Stan's criminal trial begins, law enforcement tests the DNA samples they collected. The DNA samples do not match Stan's DNA profile.

In this situation, law enforcement will drop their charges against Stan since the DNA evidence proves his innocence.


Suppose law enforcement arrested Ben for the alleged sexual assault and murder of his neighbor in 1970. At the crime scene, law enforcement collected blood and hair samples. At his criminal trial Ben testified he did not commit the crime, but a jury convicted Ben and the judge sentenced him to life imprisonment.

Fast-forward to 2023. A law enforcement agency, such as the Federal Bureau of Investigation (FBI), reopens the case. The FBI's crime lab tests the evidence collected from the crime scene in 1970 and compares it to Ben's DNA profile. They discover the DNA samples do not match. They run the DNA sample from the crime scene through a DNA index system and find it matches another person, a convicted sex offender. The FBI confronts the sex offender, who confesses to the murder committed in 1970.

In a situation like this, the court will exonerate Ben and will absolve him of any criminal wrongdoing regarding the murder.

The Innocence Project

Peter Neufeld and Barry Scheck, public defenders in New York, created the Innocence Project in 1992. The Innocence Project works to exonerate people using post-conviction DNA testing.

The Innocence Project's first client exonerated was Glen Woodall in 1992. He served five years in prison after the government wrongfully accused him of sexual assault. A jury convicted him after witnesses misidentified him. The Innocence Project proved the government engaged in misconduct and relied on flawed serology and hair analysis tests.

In 1993, the Innocence Project helped exonerate its first death row client. The Innocence Project used post-conviction DNA evidence to exonerate Kris Bloodsworth, a man convicted of sexual assault and murder.

As of 2023, the Innocence Project's work has resulted in the exoneration of 199 clients due to post-conviction DNA evidence. It has earned 245 legal victories for its clients, some of which do not include post-conviction DNA evidence. Of the 245 exonerees, 9% involved people on death row, and 5% had given false confessions and pled guilty to their charges.

DNA Evidence And the Death Penalty

Opponents of capital punishment have pushed for more frequent use of DNA testing. Even supporters of capital punishment have agreed that those convicted of a capital offense should be allowed to make use of all evidence. One of the fears that always accompanies the use of capital punishment is that the jury may sentence an innocent person to death.

One case highlighting this concern involved a man accused of murdering his sister-in-law in Virginia in 1992. The execution of Roger Keith Coleman gained national attention years later. In 2005, Governor Mark Warner of Virginia ordered DNA testing on a 24-year-old DNA sample to determine whether Coleman committed the murder.

Coleman had proclaimed his innocence throughout the case. Forensic analysts tested the DNA before his execution. Following national media attention, law enforcement decided to test the DNA again. Using more advanced technology, forensic analysts retested it. In January 2006, Governor Warner announced the results confirmed that Coleman was the killer.

Supporters of capital punishment responded, arguing that claims of the death penalty's fallibility were unfounded. Opponents noted that the danger of a wrongful execution still existed, and they continued their call for the increased use of DNA as an identification tool.

Have Questions About DNA as an Exoneration Tool? Talk to an Attorney

When you face criminal charges, your case's outcome depends on the evidence presented at trial. DNA evidence, in particular, is a powerful tool in any case. Your case will also depend on the expertise of your criminal defense attorney, some of whom specialize in DNA evidence cases. Reach out to a criminal defense attorney to discuss your case and find out how they can help.

Was this helpful?

Can I Solve This on My Own or Do I Need an Attorney?

  • Complex criminal defense situations usually require a lawyer
  • Defense attorneys can help protect your rights
  • A lawyer can seek to reduce or eliminate criminal penalties

Get tailored advice and ask your legal questions. Many attorneys offer free consultations.


If you need an attorney, find one right now.