Faulty Forensics:
Spotlight on
Firearm Analysis
Firearm identification compares ammunition samples to determine if they were fired from the same firearm or not.
In the criminal context, examiners compare ammunition found at a crime scene (the questioned sample) to ammunition test fired from a suspect's firearm (known sample).
This is based on the premise that firearms leave unique tool marks on ammunition casings and bullets. To accurately judge whether ammunition was fired from the same firearm, examiners compare individual characteristics left on ammunition, such as breech face and firing pin aperture marks.
These methods have yet to be sufficiently validated through well-designed research.
Closed set designs do not allow for accurate validity assessments.
Open set designs are recommended to accurately assess validity -- where each unknown can be a true match or non-match to a known sample. Many studies examining the validity of firearm identification use closed set designs though, where all questioned samples match one of the known samples -- making it impossible for examiners to make correct non-match decisions and determine a false positive rate.
Inconclusive judgments can misrepresent how accurate examiners are.
Inconclusive judgments also pose problems for how this science is presented in court. These are valid responses, as examiners should only make conclusions if they feel there is sufficient information to base it off of. However, since these are not counted as incorrect, examiners may over-rely on this option as an "easy out" to prevent themselves from making an error.
27% of firearm study judgments were inconclusive
Inconclusive firearm study judgments can mislead jurors
Firearm I.d. Case Study:
Odell Adams
In August 2022, CIFS collaborated with the Forensic Justice Project on an amicus brief in Odell Adams’ case to the Court of Appeals of the State of Oregon to raise the issue of pattern matching in cases involving firearms.
On May 29th, 2025, the Court of Appeals for the State of Oregon agreed that firearm and toolmark pattern matching do not meet the requirements of admissibility under Daubert.
Adams’ case was featured in the 2023 docu-series, CSI on Trial, and the corresponding podcast.
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