DNA evidence is solid evidence that can assist investigators in identifying possible perpetrators of a crime, as well as eliminating individuals who may have been falsely accused of a crime.
How investigators use DNA
Blood, clothing, chewing gum, saliva, hair and cigarette butts are items that may be left behind at a crime scene. These items may help detectives determine who was present at the crime scene. DNA, or deoxyribonucleic acid, is a unique fingerprint found in cells throughout the human body. Only a trace amount of DNA may be needed to obtain a DNA profile, which is typically compared to DNA samples from known individuals.
Solving cases without a suspect
Forensic scientists at the State Crime Lab use DNA evidence to help law enforcement solve crimes without an apparent suspect. For example, in a rape case, a victim may be unable to identify the attacker. A sexual assault kit collected from the victim may yield evidence that allows Forensic Scientists to produce an unknown DNA profile.
These unknown DNA profiles are then searched through the Combined DNA Index System (CODIS), which is a national DNA database of convicted offenders, arrestee samples, and unknown forensic DNA samples. If the search yields a "hit", the victim's attacker may be brought to justice.
Confirming suspects and clearing the wrongly accused
experts at the Crime Lab can also help when investigators have identified a potential suspect in a crime. Analysts can compare the suspect's DNA to the DNA profile left behind on a piece of evidence recovered from the scene of the crime. Results can assist investigators in determining if the suspect was involved in the crime, or can help clear someone wrongly accused.
DNA emphasis solves cases
Expert analysis of DNA evidence aids between 200-300 investigations annually as a result of CODIS "hits", which help local law enforcement officers solve murders, rapes, robberies, and other crimes across North Carolina.
Attorney General Josh Stein and the State Crime Lab have led a dramatic increase in the use of DNA technology by:
1) Expanding the state DNA database to include all convicted felons, and certain arrestees;
2) Analyzing no-suspect rape cases and subsequently searching developed unknown profiles against the CODIS database to identify potential suspects;
3) Speeding the review, audit, and uploading of convicted offender samples into the DNA database.