Document Category: Ballistics

This motion seeks exclusion of firearm and toolmark identification evidence under Daubert and Michigan Rule of Evidence 702, arguing that the AFTE method lacks foundational scientific validity and relies on subjective, unarticulated examiner judgment. Drawing on the National Academy of Sciences and President’s Council of Advisors on Science and Technology reports, the motion explains that the field lacks standardized protocols, reproducible methods, and reliable error rates, with some studies documenting false positive rates as high as 11.2 percent. The motion further argues that such evidence misleads jurors by cloaking opinion testimony as scientific and should also be excluded under Rule 403. Defenders can use this motion to demand Daubert hearings, limit examiner testimony, or seek outright exclusion of firearm and toolmark evidence.

This brief explains why expert testimony on firearm and toolmark (FA/TM) identification should be excluded. FA/TM identification is premised on the unproven assumption that each firearm leaves unique, accidental, and individualized markings on spent ammunition despite evidence from several studies that this analysis lacks sound estimates of error rates, is characterized as subjective pathological science, and is not based on reliable scientific principles. This brief collects empirical studies and evidence demonstrating that FA/TM identification lacks scientific validity (pp. 14-22), and it explains the methodological problems and high error rates associated with various studies used to attempt to validate FA/TM identification (pp. 22-43). Because of the imprecise and problematic nature of FA/TM identification, the brief also contends that experts should not be allowed to testify about characteristics of spent ammunition that imply a match (pp. 49-59).

This brief follows an extensive Frye hearing on bullet matching evidence and incorporates extensive criticism from the scientific community, an explanation of the unintended impact that a narrow definition of the “relevant scientific community” can have, and evidence of the ways that cognitive bias impermissibly taint pattern-matching evidence.

Overviews shortcomings in firearm/toolmark analysis, specifically argues against any testimony of a “match”