Third-party information in retrospective assessment of NGRI: Impact of source and supportive versus contradictory content

Experimental conditions utilizing three types of third-party information (TPI) that supported or countered a psychologist's opinion regarding insanity were compared for differential effects in a mock jury decision-making case. Collapsed conditions of TPI that provided evidence appearing to support a psychologist's opinion that a defendant met criteria for not guilty by reason of insanity (NGRI) did result in higher levels of agreement with that opinion than collapsed conditions appearing to contradict the psychologist's opinion of insanity in the defendant. However, the influence of TPI was significant depending on whether participants had initially agreed or disagreed with the psychologist's opinion. Although hypothesized to be the case, mental health records did not influence mock jurors' decisions to a greater extent than evidence from an eyewitness to the killing or the defendant's brother's opinion of the defendant's mental condition preceding the killing. These findings need to be replicated, but further research should also vary order effects and assess more explicitly the participants' reasoning for their decisions when confronted with inconsistent evidence.