Conventional wisdom maintains that the “bluff” — an interrogation technique in which investigators state they have potentially damning evidence but do not claim that this evidence implicates the accused — is of little concern to the innocent falsely accused but can frighten the guilty into confessing. According to The Innocence Project, however, approximately 25% of convicted criminals ultimately exonerated had, in fact, confessed to the crime, as The Economist notes.
A 2010 study from CUNY’s John Jay College of Criminal Justice published in Law and Human Behavior, “Inside Interrogation: The Lie, the Bluff and False Confessions (PDF),” describes a series of laboratory experiments that test how the bluff technique correlates with confessions gained from innocent parties. Subjects were instructed to complete a task, then were falsely accused of a transgression such as crashing the computer or collaborating with a colleague to improve their task performance. The experiment introduced variables such as bluff evidence, false evidence and less-than-honest eyewitnesses to identify which were the most likely to prompt a confession.
Key study highlights include:
- In the first test group, 43 of 71 subjects confessed to the experimenter that they had pressed a computer key they had been instructed to avoid when, in fact, they had not; an additional 10% admitted to pressing the key to a study observer. A second group that tested subject reactions to charges of cheating produced nearly identical percentages of false confessions.
- In the first test group, “introduction of an innocence-affirming witness did not bluff participants from the accusations and pressures of the situation.”
- In the second test group, “94% of participants expressed some degree of certainty in their own innocence: 24 (73%) were completely certain, 7 (21%) were somewhat to mostly certain; 2 (6%) said they were somewhat certain of their guilt. Despite the fact that most participants knew they were innocent, however, a majority agreed to confess.”
- In the second test group, “75% of those who confessed in the bluff condition explicitly cited the bluff as the reason for that decision.” Reasons cited for the confession included wanting to finish the study and feeling sorry for the experimenter.
- Ninety percent of subjects who believed that a hidden camera had captured their actions confessed, while only twenty-seven percent of control subjects did.
The study’s authors note that “innocent people who stand accused believe that their innocence will become apparent to others … which leads them to waive their Miranda right to silence and to an attorney.” However, they conclude that these experiments “convincingly demonstrate that use of the bluff tactic in an interrogation can induce compliant false confessions from innocent people. Importantly, however, additional research is needed to reassess the predicted effectiveness of the bluff on the true confession rates of perpetrators.”