Adversarial Allegiance: The Devil Is In The Evidence Details, Not Just On The Witness Stand.

This study examined the potential influence of adversarial allegiance on expert testimony in a simulated child sexual abuse case. A national sample of 1 witness suggestibility experts reviewed a police interview of an alleged 5 year-old female victim. Retaining party (prosecution, defense) and interview suggestibility (low, high) varied across experts. Experts were very willing to testify, but more so for the prosecution than the defense when interview suggestibility was low and vice versa when interview suggestibility was high. Experts' anticipated testimony focused more on pro-defense aspects of the police interview and child's memory overall (negativity bias), but favored retaining party only when interview suggestibility was low. Unlike prosecution-retained experts who shifted their focus from pro-defense aspects of the case in the high suggestibility interview to pro-prosecution aspects in the low suggestibility interview, defense experts did not. Blind raters' perceptions of expert focus mirrored those findings. Despite an initial bias toward retaining party, experts' evaluations of child victim accuracy and interview quality were lower in the high versus low interview suggestibility condition only. Our data suggest that adversarial allegiance exists, that it can (but not always) influence how experts process evidence, and that it may be more likely in cases involving evidence that is not blatantly flawed. Defense experts may evaluate this type of evidence more negatively than prosecution experts due to negativity bias and positive testing strategies associated with confirmation bias.