The FBI’s CODIS program is an extremely powerful crime-solving tool. By scanning through law enforcement DNA databases, it can identify the perpetrators of violent crimes or tie seemingly unconnected crimes together.
The Combined DNA Index System, known as "CODIS," is a DNA indexing program run by the FBI. Anytime a person is convicted of a serious felony nationwide, their DNA is taken and submitted to police DNA databases (these are known as "offender profiles"). Likewise, anytime a DNA profile believed to be from the perpetrator is collected from a crime scene, that too is submitted to police DNA databases (these are known as "forensic profiles"). CODIS scans through the profiles in these databases daily and identifies any that match.
Today, CODIS contains over 25 million DNA profiles, making it an extremely powerful tool for solving crimes—specifically violent crimes, since these are the sorts of crimes that tend to have DNA collected at the crime scene. Where a forensic profile matches to an offender profile, CODIS can help identify the perpetrator of the crime. And where a forensic profile matches to another forensic profile, CODIS can help tie seemingly unconnected crimes together to aid law enforcement in solving them. To date, CODIS has generated more than 750,000 hits in over 700,000 criminal cases.
When CODIS identifies a match (known as a "hit"), it notifies the crime lab that processed the DNA profile involved. Normally this crime lab is housed within a state police agency, but in some states local police departments have their own crime labs submitting to CODIS too. The crime lab reviews the hit and then notifies the law enforcement agency that submitted the profile. It is then up to that submitting law enforcement agency to take the appropriate next steps, such as investigating the hit to determine its significance, notifying victims, etc.