In phase I of the study, 104 introductory psychology students were paired to serve as mock interrogators or suspects. Each pair was randomly assigned to 1 of 4 cells produced by a 2 (interrogator expectation, guilty vs. innocent) x 2 (suspect status, guilty vs. innocent) factorial design (n=13 pairs per cell). The 52 suspects, who were assigned a guilty or innocent status in a mock theft, were questioned by 52 interrogators who were manipulated to believe that most suspects were guilty or innocent. This phase found that interrogators who believed the suspect was guilty selected more guilt-presumptive questions, used more interrogation techniques, and exerted more pressure to obtain a confession than did the interrogators who believed the suspect was innocent. In phase II, 78 introductory psychology students were paired and randomly assigned to listen to taped sessions of interrogators only, suspects only, or both tracks of 4 interrogations (1 from each cell of the 2 x 2 design). Participants decided whether each suspect was guilty or innocent and rated their confidence in that judgment. They were also asked to indicate whether the interrogator had judged the suspect guilty or innocent and their confidence in that judgment. To determine whether participants could discern interrogators' initial expectations, they rated the degree to which the interrogator presumed the suspect's guilt at the outset. They rated the interrogator's persistence and intensity in the effort to get a confession and how much pressure the interrogator put on the suspect. Regarding the suspect, participants rated how anxious and defensive he/she was, how firmly he/she denied the accusation, and how plausible his/her alibi was. The results show that the participants tended to rate as guilty those suspects presumed to be guilty by the interrogator. By neglecting to account sufficiently for the way in which the suspect's behavior was influenced by the situation and the interrogator's tactics, the participants thus committed the attribution error or correspondence bias (Gilbert and Malone, 1995; Jones, 1990; Ross, 1977). Thus, interrogations of suspects based on the interrogator's presumption of the suspect's guilt sets in motion a process of behavioral confirmation through which expectations influence the interrogator's behavior, the suspect's behavior, and ultimately the judgments of neutral observers of the interrogation process. 2 figures and 39 references