AFIS works like this: a latent print that cannot be defined as to which hand or finger (left or right) comes into the fingerprint unit. The examiner must then evaluate whether or not the print meets the standards to scan and upload it; if enhancement is required, the examiner must do that first. The print is then scanned and entered into the system. The software will then compare that print to all other prints stored in the database. The software usually suggests multiple possible matches and sorts them in order of most likely to least likely. Still, the machine can't do it all. The results from the system are then evaluated by the examiner, requiring a combination of experience, training, and visual inspection. The examiner makes the final judgment as to whether a match has been found.
CODIS, or Combined DNA Index System, is a little more complex. When it comes to criminal investigations, there are three main indexes utilized by law enforcement: offender profiles of those convicted of crimes; arrestee profiles of suspects, and forensic profiles collected from crime scenes. The purpose of this database is to link crimes to other crimes and offenders. There are other indexes as well, such as missing persons and unidentified human remains. CODIS differs from AFIS with regard to privacy: there are no personal identifiers, no names attached to these profiles. If the software finds a match, the uploading agency is notified and is then tasked with the dissemination of personal information.
It is estimated that there are over 13 million offender profiles, more than 3 million arrestee profiles, and 840,000 forensic profiles in the system as of 2018.