Document Category: Cognitive Bias

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 draft motion relies on social science about the effectiveness of mental imagery techniques at combatting implicit biases to argue for a proposed criminal jury instruction that employs a “cloaking” or “perspective-switching” exercise in which jurors are asked to consider if their impressions of the defendant (or a witness) would change if they were a different race. The draft motion collects research showing how pervasive implicit racial bias is, how voir dire alone is ineffective at ensuring defendants get fair trials, and how effective mental imagery exercises can be.  It also explains how other jurisdictions already have mental imagery instructions.

This motion argues for the exclusion of opinion testimony by medical examiners on the manner of death in a homicide trial under both the rules of evidence and the Sixth Amendment jury trial right. It explains that medical examiners speculate as to the “manner” of death based on extraneous information provided to them, notes that these determinations are not based on science, and emphasizes that there is “no standardized or validated system” for making these judgments (pages 18-23). The motion also cites cognitive science in support of the claim that biases, including racial biases, can shape these “manner of death” determinations (pages 23-24). Attached to the motion are (1) transcripts of interviews with two medical examiners, exposing the problems with manner of death determinations; (2) an expert report and law review article detailing the cognitive science problems with these determinations; (3) the non-scientific manual used to instruct medical examiners on how to make these determinations; and (4) a letter signed by 86 forensic pathologists and death investigators about judicial misuse of manner of death determinations.

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.

This motion relies on federal rules of evidence and Daubert to argue that a physician should not be permitted to testify that a person died from an oxycodone overdose when there are alternative potential causes of death – such as cardiac arrhythmia – that have not be properly eliminated. More generally, the motion explains when doctors who rely on differential diagnosis – the process of identifying the cause of a medical problem by eliminating likely causes until the most probable one is isolated – are conducting a reliable, medical analysis versus when their analyses are compromised by cognitive biases. The social science collected in this motion would be useful to defenders challenging the validity of any causal conclusion physicians reach.

Pages 4-6 explain the differential diagnosis process and how it can lead physicians to make unreliable conclusions about cause of death.  Pages 6-17 discuss how cognitive biases like confirmation bias, role effects, the availability heuristic, and the representativeness error can infect differential diagnoses.  Pages 17-20 talk about when differential diagnoses are unreliable due to a physician’s failure to properly rule in certain causes and rule out potential alternatives.  Pages 20-24 draw analogies to the forensic sciences and argue that the physician in this case could testify that there was oxycodone in the patient’s system but should not have been able to opine with certainty that it caused the patient’s death.  Pages 24-28 explain why the doctor’s ultimate opinion invaded the province of and was unhelpful to the jury.

Filed by the Center for Integrity in Forensic Science, this brief explains the research demonstrating that cognitive bias in forensic analysts contributes to unreliable conclusions.

Transcript of testimony and argument pursuant to the defense motion to exclude the government’s expert witness. Defense witness explains (with research studies as examples) confirmation bias, contextual bias, and exposure to task-irrelevant information. Arguments: p. 57-70.