Returning now to our original question of whether the probative value of videotape and computer-animated demonstrative evidence is outweighed by its prejudicial impact, we believe it is too early to provide a definitive answer. Clearly, research has shown that demonstrative evidence has the potential both to inform and prejudice jurors. In at least one study, mock jurors made better decisions when they viewedphysical evidence that was accompanied by computer-animated demonstrative evidence than when it was not (Kassin and Dunn, 1997). That is, computer animation helped mock jurors to make decisions that were more consistent with the physical evidence of the case. However, demonstrative evidence that is inconsistent with physical evidence could negate or even reverse any potential beneficial effects of demonstrative evidence. For example, participants in one study who viewed a computer animation depicting a victim's 'fall' ignored contradictory testimony and physical evidence indicating that the body landed 20-25 feet away from the building (Kassin and Dunn, 1997).
The Kassin and Dunn (1997) findings have important implications for the role of judges and attorneys in trials in which videotape or computer-animated testimony is proffered. First, judges must carefully scrutinize the content and nature of demonstrative evidence to ensure its reliability. Are the essential ingredients ofthe videotape simulation or computer animation supported by other known facts or credible evidence?
Does the demonstrative evidence represent a reasonable depiction of the alleged event? If the videotape or computer animation incorporates physics theorems or mathematical models, is that information accurately portrayed? Second, attorneys must attend to the reliability of proffered videotape and computer-animated demonstrative evidence as well. If opposing counsel fails to raise and substantiate a valid objection to the admission of unreliable demonstrative evidence (e.g. inconsistency between the physical facts and the videotaped or computer-animated simulation), judges most likely will admit the evidence without question. Moreover, if inconsistent or exaggerated demonstrative evidence is admitted, opposing counsel must discover these defects in order to bring them to the jurors' attention through rigorous cross-examination (assuming that expert testimony accompanies the demonstrative evidence) or in closing arguments. Thus, it behooves both judges and attorneys to scrutinize videotape and computer-animated demonstrative evidence to ensure that these media are consistent with any known physical evidence in the case.
Assuming that attorneys objectto unreliable demonstrative evidence andjudges refuse to admit it, one question that remains is whether reliable videotape and computer animations are more probative than prejudicial relative to oral testimony in cases involving evidence more ambiguous than that included in Kassin and Dunn (1997). In those cases, we can expect attorneys zealously advocating for their clients to present theories or versions of the evidence in a manner that benefits their clients the most. Do judges need to be more concerned about technologically advanced methods of depicting theories than they are about traditional methods, such as oral arguments and testimony? Future research should better address this question by covarying the evidence presentation format (demonstrative evidence versus oral testimony) and the nature of that evidence (ambiguous versus concrete). It also will be important to discover the effects of videotape and computer-animated demonstrative evidence presented at different points during the trial (opening statements versus closing arguments) by different sources (attorney versus expert). Moreover, studies should investigate judges' and jurors' thresholds for taking demonstrative evidence into account. At what point do judges and jurors perceive that demonstrative evidence is too suggestive or too speculative and thus disregard it? Do judicial instructions clarifying the nature of demonstrative evidence (i.e. to present one side's theory or version of the facts) help sensitize jurors to unreliable or extremely suggestive demonstrative evidence? Finally, should jurors be allowed to take videotape and computer-animated demonstrative evidence with them into the deliberation room for additional viewing? In the interim, it appears that at least one form of technologically sophisticated demonstrative evidence (computer animations) can both enhance and bias juror decision-making in certain circumstances.
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