Witness preparation training with real and simulated criminal defendants.

Two studies examined the impact of witness preparation training with criminal defendants. In the first study, mock criminal defendants testified twice on videotape about minor crimes they were accused of but had not committed. Approximately half underwent witness preparation between their first and second testimony simulations. In the second study, eight public defender clients were videotaped during testimony simulations both before and after being prepared to testify. In both studies, ratings by trained evaluators indicated that witness preparation was associated with increases in the use of several testimony delivery skills, improvements in overall testimony quality, and reductions in apparent guilt. Training was also associated in both studies with an unintended decrease in expressiveness. Ratings from the mock defendant study further suggested that prepared defendants were seen as more credible than unprepared defendants because they used more effective testimony delivery skills, and as less likely to be guilty than unprepared defendants because they were perceived as being more credible.