It is easier to exclude a suspect than to convict someone based on a DNA match. The FBI estimates that one-third of initial rape suspects are excluded because DNA samples fail to match.
Forensic DNA is just one of many types of evidence. Investigators also look at other clues, such as motive, weapons, alibis, and additional evidence linking a suspect to the crime scene. When multiple lines of evidence tell a consistent story, investigators can be assured that samples from a particular suspect were not planted, either on purpose or by accident, at the crime scene.
Can DNA evidence exonerate wrongfully convicted prisoners?
The Innocence Project at New York's Benjamin N. Cardozo School of Law aims to exonerate prisoners wrongfully convicted of crimes. The project uses DNA profiling evidence to support the re-evaluation of criminal cases. But DNA evidence alone is not enough to get a person out of jail: the case must be re-examined by a judge, along with lawyers representing both sides of the case. Since 1992, the Innocence Project and others have used DNA evidence to exonerated over 300 prisoners, including eighteen who were on death row—one of whom was only five days from execution.
While some states will reconsider cases with compelling DNA evidence regardless of when the trial ended, several states restrict the time for post-trial submission of DNA evidence to six months or less. And unfortunately, the evidence from some cases has been lost or destroyed, making DNA analysis impossible. The Innocence Project seeks to reform the criminal justice system in ways that will improve access to DNA testing, improve evidence preservation, and permit re-evaluation of DNA evidence in closed cases.
Is DNA-profiling technology used appropriately for justice?
DNA profiling can be a powerful tool in criminal investigations. Its success in the courtroom depends upon many factors, including:
- Proper handling of evidence
- Careful analysis by an unbiased forensic laboratory
- Fair and appropriate interpretation of the results
- Accurate and effective reporting of results to judges and jurors
When used correctly, DNA profiling is a powerful forensic tool. It can be used to quickly eliminate a suspect, saving time in searches for perpetrators. And it can provide compelling evidence to support a conviction and, most importantly, reduce the chances of a wrongful conviction.