In Brief

Jurors may be highly susceptible to issuing unfair verdicts due to "predecisional distortion," the tendency to view each new piece of evidence with a bias toward the party that the juror favors, according to a study at Cornell University.

"Biased interpretation of evidence by mock jurors," by Kurt A. Carlson and J. Edward Russo, PhD, of Cornell's Johnson Graduate School of Management, raises concerns about conventional pretrial instructions to jurors and advocates alternative pretrial procedures.

In their study, Carlson and Russo evaluated the effect of jurors' personal beliefs on verdicts by using two sample groups: one of university students and another of potential jurors, ages 40 to 45. All participants viewed a video explaining the importance of refraining from making decisions before all of the evidence was presented. Participants were then given affidavits, case backgrounds and opening arguments and asked to assess whether the plaintiff or defendant benefited from each.

The researchers found that 75 percent of students and 85 percent of potential jurors exhibited predecisional distortion: The typical participant evaluated new evidence as too supportive of whichever party was leading in his or her mind when the new evidence was encountered.

Predecisional distortion builds upon the story theory, which states that people have a need to view a coherent world; thus jurors will create narratives based on their own experiences to make the facts of a case understandable to themselves.

Carlson and Russo believe that the judicial system could circumvent this bias by integrating information about predecisional distortion in jurors' pretrial instructions so that they can be more conscious of how they analyze evidence. Humans have a natural tendency to favor the "leader" and so unfairly view new evidence as supporting the party that currently appears stronger. Carlson suggests that an individual who is aware of this bias can compensate for it.

The study appeared in the Journal of Experimental Psychology: Applied (Vol. 7, No. 2).