John Collins, President, Forensic Foundations Group
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On Bias in Forensic Science National Commission on Forensic Science – May 12, 2014 56-year-old Vatsala Thakkar was a doctor in India but took a job as a convenience store cashier to help pay family expenses. She was stabbed to death outside her store trying to thwart a theft in November 2008. Bloody Footwear Impression Bloody Tire Impression What was the threat? 1. We failed to ask ourselves if this was a footwear impression. 2. The appearance of the impression combined with the investigator’s interpretation created prejudice. The accuracy of our analysis became threatened by our prejudice. Types of Cognitive Bias Available at: http://en.wikipedia.org/wiki/List_of_cognitive_biases | Accessed on April 14, 2014 Anchoring or focalism Hindsight bias Pseudocertainty effect Illusory superiority Levels-of-processing effect Attentional bias Hostile media effect Reactance Ingroup bias List-length effect Availability heuristic Hot-hand fallacy Reactive devaluation Just-world phenomenon Misinformation effect Availability cascade Hyperbolic discounting Recency illusion Moral luck Modality effect Backfire effect Identifiable victim effect Restraint bias Naive cynicism Mood-congruent memory bias Bandwagon effect Illusion of control Rhyme as reason effect Naïve realism Next-in-line effect Base rate fallacy or base rate neglect Illusion of validity Risk compensation / Peltzman effect Outgroup homogeneity bias Part-list cueing effect Belief bias Illusory correlation Selective perception Projection bias Peak-end rule Bias blind spot Impact bias Semmelweis reflex Self-serving bias Persistence Choice-supportive bias Information bias Social comparison bias Shared information bias Picture superiority effect Clustering illusion Insensitivity to sample size Social desirability bias System justification Positivity effect Confirmation bias Irrational escalation Status quo bias Trait ascription bias Primacy effect, Recency effect & Serial Congruence bias Just-world hypothesis Stereotyping Ultimate attribution error position effect Conjunction fallacy Less-is-better effect Subadditivity effect Worse-than-average effect Processing difficulty effect Conservatism or regressive bias Loss aversion Subjective validation Bizarreness effect Reminiscence bump Conservatism (Bayesian) Mere exposure effect Survivorship bias Choice-supportive bias Rosy retrospection Contrast effect Money illusion Time-saving bias Change bias Self-relevance effect Curse of knowledge Moral credential effect Unit bias Childhood amnesia Source confusion Decoy effect Negativity effect Well travelled road effect Conservatism or Regressive Bias Spacing effect Denomination effect Negativity bias Zero-risk bias Consistency bias Spotlight effect Distinction bias Neglect of probability Zero-sum heuristic Context effect Stereotypical bias Duration neglect Normalcy bias Actor-observer bias Cross-race effect Suffix effect Empathy gap Observation selection bias Defensive attribution hypothesis Cryptomnesia Suggestibility Endowment effect Observer-expectancy effect Dunning–Kruger effect Egocentric bias Telescoping effect Essentialism Omission bias Egocentric bias Fading affect bias Testing effect Exaggerated expectation Optimism bias Extrinsic incentives bias False memory Tip of the tongue phenomenon Experimenter's or expectation bias Ostrich effect False consensus effect Generation effect (Self-generation effect) Verbatim effect Functional fixedness Outcome bias Forer effect (aka Barnum effect) Google effect Von Restorff effect Focusing effect Overconfidence effect Fundamental attribution error Hindsight bias Zeigarnik effect Forer effect or Barnum effect Pareidolia Group attribution error Humor effect Framing effect Pessimism bias Halo effect Illusion of truth effect Frequency illusion Planning fallacy Illusion of asymmetric insight Illusory correlation Gambler's fallacy Post-purchase rationalization Illusion of external agency Lag effect Hard-easy effect Pro-innovation bias Illusion of transparency Leveling and Sharpening National Institutes of Health “Bias is defined as any tendency which prevents unprejudiced consideration of a question.” National Institutes of Health “Bias is defined as any tendency which prevents unprejudiced consideration or answering of a question.” 1996 Olympic Bombing - Atlanta John Iacono Julian Gonzalez/Black Star Photos available at: http://sportsillustrated.cnn.com/events/1996/olympics/weekly/960805/tragedy.html Stamped Surface Masonry Nails (impressions) Analysis by Jerry Miller, ATF Lab Atlanta Cut surface Cut surface (striations) (striations) Nails from the Olympic Bomb were cut by the same machine as nails found at Eric Rudolph’s residence. What was the threat? The associative power of the identical toolmark patterns would have been easy to over-state into a compelling case of guilt. We must respect the threat of bias, know where it lives, and what may cause it to strike. We respect it, but we don’t fear it. We mitigate the risk. Where the threat “lives” in forensic science 1. Subordinate employees conducting quality assurance checks for their supervisors. 2. Wanting to please the “customer.” 3. Allowing scientific meaning to be lost in legal translation – “zealous advocacy” 4. Ambiguity / variance in reporting (written/oral). Comparative Severity Bias/Human Factors Pressure/Neglect of the Forensic Science Less prepared Workforce Photos available at: http://jimburnsphotos.com/media/Western-Diamond-backed-Ratt.jpg and http://lovellchronicle.blogspot.com/2010/05/freight-train-derails-at-wind-river.html Culture, Values, and Communication Outliers by Malcolm Gladwell “The kinds of errors that cause plane crashes are invariably errors of teamwork and communication. One pilot knows something important and doesn’t tell the other pilot. One pilot does something wrong, and the other pilot doesn’t catch the error. A tricky situation needs to be resolved through a complex series of steps – and somehow the pilots fail to coordinate and miss one of them.” A Final Thought Dr. Peter F. Gerhardt, Researcher “The interplay between choice and control is called competence.” On Bias in Forensic Science National Commission on Forensic Science – May 12, 2014 .