The current study extends previous research demonstrating the detrimental effects of divided attention during encoding on eyewitness memory. Previous data indicate that judging the veracity of a suspect causes witnesses to scrutinize him or her carefully and requires relatively high cognitive effort. We therefore hypothesized that performing this task while simultaneously observing the suspect should impair witnesses' memory for his or her appearance and message while ironically inflating their certainty and other testimony‐relevant judgments. Our results supported these predictions. Moreover, inducing witnesses to be suspicious about the suspect's truthfulness (Experiment 1) and motivating them to judge veracity as accurately as possible (Experiment 2) amplified the memory impairment effect and further increased several testimony‐relevant ratings. Additionally, compared with witnesses who incorrectly identified the suspect in a line‐up, those who made a correct decision expressed greater certainty about their line‐up accuracy and also provided higher ratings on some other testimony‐relevant measures. Copyright © 2013 John Wiley & Sons, Ltd.