1. Everyone assumes there is a single database for fingerprints in the United States and you just input your unknown print and it searches all.
A. Discuss why elimination prints are necessary both to solve a case and to avoid issues at trial.
B. What is the database for fingerprints and how does this assist in the identification process?
2. You are the District Sergeant in charge. There is a new housing development being built. There will be 150 new homes constructed over the next 2 years. Several houses have had their new appliances stolen before the Certificate of Occupancy was issued. What are some of the issues with fingerprints you may lift from the scene?
3. Research and share how latent prints have been utilized in solving historical crime
Sample Answer
Fingerprint Databases and Elimination
A. The Necessity of Elimination Prints
Elimination prints are known samples taken from people who had legal access to a crime scene (e.g., the victim, family members, or first responders). They are vital for two reasons:
Solving the Case: In a typical scene, dozens of prints are left behind. Without elimination prints, analysts waste weeks processing "noise"—prints belonging to the homeowner or a roommate. By "eliminating" the known residents, investigators can focus exclusively on the unidentified latent prints, which are significantly more likely to belong to a suspect
Avoiding Issues at Trial: Defense attorneys often use the presence of unidentified prints to create "reasonable doubt," suggesting that the "mystery print" belongs to the real killer. If the prosecution can demonstrate that every print at the scene was accounted for through elimination (proving the mystery print belongs to the defendant), the case becomes much stronger.
B. The Database: NGI (formerly IAFIS)
Contrary to the "single database" myth, the primary system used is the Next Generation Identification (NGI) system, managed by the FBI.
How it assists: NGI is a multi-modal biometric database. When a latent print is recovered, it is uploaded into the system, which uses complex algorithms to provide a "Candidate List" of potential matches based on minutiae (ridge endings, bifurcations).
The Human Element: The computer does not make the final "match." A certified latent print examiner must manually compare the unknown print against the top candidates provided by the system using the ACE-V method.
2. Sergeant’s Briefing: Issues with Construction Site Prints
As the District Sergeant, you must manage expectations regarding prints recovered from new housing developments. The "appliance theft" scenario presents several unique forensic challenges: