When do stereotypes and biases affect judgments of alibis and crime suspects? Two studies addressed this question. Undergraduates (N- 192 in Study 1, N= 339 in Study 2) listened to an audio-taped police interview with a suspect concerning his/her alibi. Participants then rated the believability of the alibi and the likelihood that the suspect was guilty. The impact of: (1) the strength of the evidence that supported the alibi; (2) characteristics of the suspect (e.g., gender, attractiveness, and prior convictions); (3) judge's instructions on prior conviction evidence; and (4) perceivers' motivation to process the alibi (using scores on the Need for Cognition Scale) on alibi believability and likelihood of suspect guilt ratings was studied. Other dependent measures were assessments of the suspect's character and participant-jurors' understanding of judicial instructions. It was found that the suspect's gender and level of physical attractiveness did not affect alibi believability and guilt ratings, but were important when it came to assessing the suspect's character. Participants took the defendant's prior record into consideration when assessing guilt: Defendants previously convicted of the same crime as the current charge were seen as more likely to be guilty than defendants previously convicted of a different crime. Judge's instructions did not affect guilt ratings, which suggests that participants did not use the prior conviction evidence as they had been instructed. In contrast to predictions, need for cognition played less of a role in terms of alibi believability ratings and guilt judgments. However, NFC did affect participants' understanding of judicial instructions and their recall of those instructions. The two studies suggest that alibi strength consistently influences believability and guilt ratings. Strong alibis were seen as more believable and led to lower guilt ratings than weak alibis. Limitations of this dissertation, legal implications, and future directions are discussed.