AFIS Accuracy and the Unidentified Latent Image

In this Blog I wanted to talk about something that would be just as useful to a prosecutor as to a defense attorney. I decided to talk about the automated fingerprint identification system and peoples assumptions of AFIS systems accuracy and potential case impact If you have latent image(s) in a case that are not identified and have been searched in AFIS, can you be sure the individual is not in the system? The answer unfortunately is no. In Omaha a couple years back a latent examiner made a latent identification on a homicide from an AFIS search, I think it may have been the 4 th. search of the system before it produced the correct suspect. The examiner understood that in some cases the latent needs to be entered and searched more than once. So if there are unidentified latents in a case, a single search of the system may not produce the identification. It would seem that in cases going to trial, the attorney would want to insure the unidentified latents be entered more than one(1) time to insure that the latent is one that does not have a match in the database What are some of the causes of the system not producing the individual?




The common assumption of the court, attorneys, jurors and many latent examiners is; AFIS systems are close to 100% accurate, so one search should suffice. Most systems today will have an accuracy less than 75 t0 80 % for latent searches. Typically the vendor will produce an accuracy 75 to 80 % if the latent image has 15 points and the target has the same 15 points. The other thing to remember about these tests are the vendor is using a small database that may not accurately reflect the a larger database of the live system. What can add to the confusion is the tenprint to tenprint accuracy which for the FBI IAFIS is 98% and most state systems probably 95%.



The other factor to remember is the system will produce a number of very good suspects which can move the suspect down the list or when dealing with poor quality images an examiner may miss the identification.

Another factor to consider, minutiae placement which is critical to any AFIS search. Minutiae can be selected by the system and manually edited by the examiner or manually selected by the examiner. Anecdotal evidence would suggest manually placing the minutiae will produce a more accurate result. Studies have shown that an examiner may vary slightly on minutiae selection the 2nd. time they see a latent print (table 3).

The results of any of the above could lead to a wrongful conviction and individual not being interviewed who may help in the investigation or an element of doubt in a jurors mind. To insure a proper AFIS search the prosecution should insure that latents that may impact a case if unidentified are searched more than one (1) time when they have their meeting prior to the court date. The defense attorney on the other hand would be the fail safe, insuring that the latent was searched multiple times.

Bob McAuley Dir. Operations/Training Forensic Biometric Identification Solutions LLC.