Cognitive Bias in Forensic Science Keith A. Findley Assistant Professor Lessons from the Innocent Eyewitness Error—76% of wrongful convictions False confessions—16%-24% of cases Erroneous forensic science—~60% of cases Jailhouse snitch testimony—18%+ of cases Prosecutorial or police misconduct Inadequate defense counsel Lessons from the Innocent Eyewitness Error—76% of wrongful convictions False confessions—16%-24% of cases Erroneous forensic science—~60% of cases Jailhouse snitch testimony—18%+ of cases Prosecutorial or police misconduct Inadequate defense counsel Tunnel Vision That compendium of common heuristics and logical fallacies, to which we are all susceptible, that lead actors in the criminal justice system to focus on a suspect, select and filter the evidence that will build a case for conviction, while ignoring or suppressing evidence that points away from guilt. Keith A. Findley & Michael S. Scott, The Multiple Dimensions of Tunnel Vision in Criminal Cases, 2006 WIS. L. REV. 291 Cognitive Biases 1 3 7 15 31 63 127 255 256 Confirmation Bias . Tendency to seek confirming, rather than disconfirming evidence Confirmation Bias A B 2 3 Hypothesis: any card with a vowel facing up has an even number on the reverse side Confirmation Bias in a Social Context Task: Determine if person is an introvert or extrovert . Subjects tasked with identifying if person was introvert consistently asked confirming questions, e.g.: . What is it about large groups that makes you feel uncomfortable? . Subjects tasked with identifying if person was extrovert asked, e.g.: . What would you do if you wanted to liven things up at a party? Confirmation Bias . Tendency to seek confirming, rather than disconfirming evidence . Tendency to recall confirming evidence in a biased manner Biased Recall . Story about a person who acted in both introverted and extroverted ways . Days later, asked to assess suitability of a person for a job that clearly required either extroversion or introversion . Those assessing suitability for extrovert’s job recalled instances of extroversion . Those assessing suitability for introvert’s job recalled introversion Confirmation Bias . Tendency to seek confirming, rather than disconfirming evidence . Tendency to recall confirming evidence in a biased manner . Tendency to interpret ambiguous evidence in manner that confirms preexisting beliefs Biased Data Interpretation . E.g., people told that a person has certain personality characteristics tend to then see those characteristics in a person, even if they are not objectively present . Effect in criminal cases: individual is being judged—by police, prosecutors, defense lawyers, judges, and jurors—where the initial working hypothesis presented to each actor in the system is often that the defendant is guilty (despite the theoretical presumption of innocence). Belief Perseverance Subjects asked to distinguish between real and fake suicide notes. Participants were given random feedback on how they were doing—unrelated to actual performance . Participants were then told the feedback was random and fake . Yet those given positive feedback continued to rate their ability much higher than those given negative feedback Belief Perseverance in Criminal Cases . Confronted with disconfirming evidence, prosecutors sometimes work hard to rationalize it away: . The “unindicted co-ejaculator” theory Confirmation Bias in Police Investigations . Police officers rate disconfirming or exonerating evidence as less reliable or credible than guilt- confirming evidence that supports their initial hypotheses . Ask & Granhag (2007); Ask, Rebelius, & Granhag(2008) . Investigators show marked confirmation bias when asked to form hypothesis of guilt early in the evaluation of evidence, as opposed to if they are not asked for a hypothesis until end of review of all evidence. O’Brien (2009) Role Effects . People’s perceptions of their role can influence their decisions • Prichert & Anderson, Taking Different Perspectives on a Story, 69 J. EDUC. PSYCHOL. 309 (1977); Anderson, Pichert & Shirey, Effects on a Reader’s Schema at Different Points in Time, 75 J. EDUC. PSYCHOL. 271 (1983); Starrs, The Ethical Obligations of the Forensic Scientist in the Criminal Justice System, 54 J. ASS’N OFFICIAL ANALYTICAL CHEMISTS 910 (1971); Risinger, Saks, Thompson & Rosenthal, The Daubert/Kumho Implications of Observer Effects in Forensic Science: Hidden Problems of Expectation & Suggestion, 90 CAL. L. REV. 1 (2002) . One of the risks of embedding forensic sciences within law enforcement . Or, conceivably, of creating special units like child abuse investigation teams Conformity Effects . The “tendency to conform to the perceptions, beliefs, and behavior of others. Research on conformity shows that people rely on the views of others in order to develop their own conclusions, sometimes to gain additional information, other times merely to be in step with their peers.” . Risinger, Saks, Thompson, & Rosenthal, The Daubert/Kumho Implications of Observer Effects in Forensic Science: Hidden Problems of Expectation and Suggestion, 90 CAL. L. REV. 1 (2002) Group Think . The opportunity for cross-talk undermines the ability to catch errors or reveal alternatives “Diagnosis Momentum” Dr. Jerome Groopman, How Doctors Think (2007): “Once a particular diagnosis becomes fixed in a physician’s mind, despite incomplete evidence—or, in [some] case[s], discrepancies in evidence—the first doctor passes on this diagnosis to his peers or subordinates. … Diagnosis momentum, like a boulder rolling down a mountain, gains enough force to crush anything in its way.” Contextual Bias . When extraneous information influences a decision, typically in cases of ambiguity . “Observer effects” Inferential Spillage Other evidence in the case (context) Hasel & Kassin (2009). On the Assumption of Evidentiary Witnesses’ Independence. confidence rose by 40% After picking a suspect at a lineup, eyewitnesses were told that the suspect they chose had confessed to the crime Inferential Spillage Other evidence in the case (context) Ask & Granhag, (2007). Motivational Biases in Criminal Investigators’ • Witness was Judgments of Witness Credibility deemed more credible A witness was interviewed • Witness was after strong incriminating deemed less evidence was already credible collected: • When the witness confirmed the suspect’s guilt • When the witness This study was disconfirmed the conducted with suspect’s guilt experienced Swedish criminal investigators Inferential Spillage Other evidence in the case (context) Hope et al., (2004). Understanding pretrial publicity: Predecisional distortion of evidence by mock jurors. Testimony of 4 witnesses was interpreted as more inculpatory (police Defendant in murder case officer, coroner, was described as an victim’s father, antisocial bully social worker) The Echo Chamber in the Tunnel Mistaken ID Tainting information Pressured given to lab Confession analysts Incentives to snitches Spillage is Stealthy People have a difficult time shielding themselves from impermissible information Inferential Spillage Inability to ignore inadmissible evidence Hope et al., (2004). Understanding pretrial publicity: Predecisional distortion of evidence by mock jurors. The pretrial publicity nonetheless Jurors told to ignore influenced the newspaper reports that testimony of 4 defendant in murder case other witnesses was an antisocial bully Inferential Spillage Inability to ignore inadmissible evidence Wallace & Kassin (2012). Harmless Error Analysis: How Do Judges Respond to Confession Errors? Their verdicts were nonetheless influenced by the Judges determined that confessions (69% certain interrogations were v. 17% conviction coercive (and thus rate) inadmissible) This study was conducted with sitting judges Spillage is Stealthy Double meta-cognitive error: . People unaware that they are susceptible to external non-normative influences . But they are! . People unaware that they engage in backward reasoning . But they do! . Stark schism between the perceived and the actual decision making process . Naïve realism; Bias blind spot . Much going on beneath the hood Bias in Forensic Science Features of Wrongful Convictions False Snitch Testimony False Confessions Forensic Science Eyewitness Error 0% 20% 40% 60% 80% Flawed Forensics Wrongful Convictions with Forensic Science Evidence Improper Testimony Improper Testimony 61% Proper Testimony 39% Source: Garrett & Neufeld, Improper Forensic Science and Wrongful Convictions, 95 Va. L. Rev. 1 (2009) What Biases Might Affect Forensic Practitioners? Robert Lee Stinson 1984 Murder in Milwaukee 1985 Conviction & life sentence The Evidence . Stinson lived next door; police focused on him because his teeth looked somewhat like odontologist’s sketch of killer’s teeth . Two forensic odontologists examined the bite marks and Stinson’s dentition. The bite marks “had to have been made by teeth identical” to Stinson’s. There was “no margin for error in this.” . The bite mark evidence was “overwhelming.” . “[T]here was no question there was a match.” DNA Testing in the Stinson Case . From cuttings from the victim’s shirt . STR . Partial, mixed profiles . All excluded Stinson . YSTR . Multiple profiles . All excluded Stinson . Subsequent STR analysis . Full male STR profile developed, not Stinson . Database hit on Moses Price . Price confessed and explained how he committed the crime Madrid Train Bombing Madrid Train Bombing March 11, 2004: terrorists kill 191 people by placing bombs on several