Do confessions taint perceptions of handwriting evidence? An empirical test of the forensic confirmation bias.

Abstract

Citing classic psychological research and a smattering of recent studies, Kassin, Dror, and Kukucka (2013) proposed the operation of a forensic confirmation bias, whereby preexisting expectations guide the evaluation of forensic evidence in a self-verifying manner. In a series of studies, we tested the hypothesis that knowing that a defendant had confessed would taint people's evaluations of handwriting evidence relative to those not so informed. In Study 1, participants who read a case summary in which the defendant had previously confessed were more likely to erroneously conclude that handwriting samples from the defendant and perpetrator were authored by the same person, and were more likely to judge the defendant guilty, compared with those in a no-confession control group. Study 2 replicated and extended these findings using a within-subjects design in which participants rated the same samples both before and after reading a case summary. These findings underscore recent critiques of the forensic sciences as subject to bias, and suggest the value of insulating forensic examiners from contextual information.

The Social Psychology of False Confessions

“…Other research has shown that a strong belief in a suspect's guilt can also bias lay people's judgments of handwriting samples (Kukucka & Kassin, ), their willingness to vouch as an alibi for a confederate (Marion et al., ), their perceptions of whether degraded speech recordings contain incriminating remarks (Lange, Thomas, Dana, & Dawes, ), and the judgments of experts who are presented with inconclusive polygraph charts (Elaad, Ginton, & Ben‐Shakhar, ) and latent fingerprint samples (Dror & Charlton, ).…”

Stigma against false confessors impacts post‐exoneration financial compensation

“…As further testament to its power, recent work has identified ways in which a confession, once obtained, alters the course of a criminal case. For example, confessions can corrupt other evidence in ways that create illusory corroboration (e.g., Hasel & Kassin, ; Kukucka & Kassin, ) while also suppressing exculpatory evidence (Marion, Kukucka, Collins, Kassin, & Burke, ). At trial, confessors may be more likely to receive ineffective counsel (Kukucka & Kassin, ) and less likely to be granted post‐conviction appeals (Kassin, ) than other defendants.…”

“…As further testament to its power, recent work has identified ways in which a confession, once obtained, alters the course of a criminal case. For example, confessions can corrupt other evidence in ways that create illusory corroboration (e.g., Hasel & Kassin, 2009;Kukucka & Kassin, 2014) while also suppressing exculpatory evidence (Marion, Kukucka, Collins, Kassin, & Burke, 2016).…”

On confirmation bias in imaging research

“…While patient selection bias is, in general, commonly acknowledged in the research community, confirmation bias can be more insidious . Confirmation bias is a type of selection bias that occurs when a particular reference standard is required for study inclusion.…”