When Self-Report Trumps Science: Effects of Confessions, DNA, and Prosecutorial Theories on Perceptions of Guilt

For many wrongfully convicted individuals, DNA testing presents a new and invaluable means of exoneration. In several recently documented cases, however, innocent confessors were tried and convicted despite DNA evidence that excluded them. In each of these cases, the prosecutor proposed a speculative theory to explain away the mismatched confession and exculpatory DNA. Three studies were conducted that pitted confessions against DNA test results. Study 1 showed that people in general trust DNA evidence far more than self-report, including a defendant's confession. Using student and adult community samples, Studies 2 and 3 showed that in cases in which the defendant had confessed to police but was later exculpated by DNA, prosecutorial theories spun to reconcile the contradiction attenuated the power of exculpatory DNA, significantly increasing perceptions of the defendant's culpability, the rate of conviction, and the self-reported influence of the confession. Implications and suggestions for reform are discussed.