The "CSI effect" is a term coined by prosecutors and the mass media to describe the influence that television crime dramas like CSI: Crime Scene Investigation have on jurors. Prosecutors, like those in the Maricopa County prosecutors’ office, argue that juries now expect to witness the same sleights of evidentiary magic in real life trials.

The CSI effect is probably most important as an example of the way that a broad consensus about the existence of a legally relevant “fact” can emerge out of unsystematic and untested anecdotal observations, in this case by prosecutors and other court observers seeking to explain acquittals that they find puzzling. Those facts can then take on a life of their own, especially when aided by the popular press. And, they can lead to arguments in favor of adopting a variety of changes in how trials are conducted and in thinking about how they might be won.

While some existing evidence, like the Maricopa study, is consistent with the CSI effect argument, it is equally plausible to argue that watching CSI has, in fact, the opposite effect on jurors--increasing their tendency to convict defendants.

For starters, if the CSI effect increases acquittals it would seem to contradict the psychological forces that make CSI one of the highest-rated shows on television. CSI is popular because it delivers certainty. We know who committed the crime and we see that that person has been identified, apprehended, and presumably will be punished. Most real-life criminal prosecutions do not fit this open-and-shut paradigm, and to the extent that watching CSI causes would-be jurors to have greater confidence the ability of investors to catch the “bad guy,” the CSI effect might actually increase their tendency to convict.

We know from the psychological literature that people want the closure of seeing the wrongdoer punished, and they are often willing to lower their standards of proof in the service of this desire. Mobs and vigilante groups, for example, drop their standard of evidence dramatically because they have an intense emotional need to punish someone for the commission of a crime.

But whether they are in an angry mob or a reflective jury, people need to have a plausible way to legitimate their guilty verdicts, and scientific evidence provides that justification. Studies by psychologists show that decisionmakers already overweigh scientific evidence relative to its actual probative value. CSI further legitimates scientific evidence and lends it a veneer of certainty and decisiveness. It facilitates the exaggeration of the probative value of science, allowing juries to achieve closure more comfortably by voting for convictions. Hence, the CSI effect may exist, but it may be the opposite of that widely presented in the mass media.

If the rate of acquittals is increasing, there may be other explanations for it besides the CSI effect itself. Juries increasingly accept excuses ranging from a “rotten childhood” to a history of being abused to mitigate responsibility for a crime. In addition, much of the prosecutor’s ability to gain a conviction depends upon the willingness of jurors to trust the credibility of the state and of its representatives, and such trust is declining. Finally, there may be no trend here at all--juries may simply be reflecting the long-observed tendency of laypeople to be more likely to acquit, at least relative to decisions made by legal authorities such as judges.

At this time there is no scientific, empirical study that determines whether the CSI effect exists, orwhat it looks like. The Maricopa County prosecutors based their study on conversations with jurors after their trials. For this type of evidence to be credible we have to believe not only that jurors can accurately tell us if their verdict was influenced by particular knowledge about standards for evaluating evidence, but also that they know whether or not they acquired their information and standards from watching CSI. Psychologists are widely skeptical about people’s self-awareness on both counts, which is why they conduct controlled experiments. An experiment directly tests whether an experience, such as watching CSI, influences decisionmaking and is not biased by whether or not jurors know why they are acting as they do.

Although any changes to the legal system would be premature at this point given the lack of hard evidence, prosecutors have proposed a variety of remedies for the CSI effect, including asking about jurors’ viewing habits during jury selection, instructing jurors not to use CSI standards when evaluating scientific evidence, training prosecutors to make more sophisticated presentations of scientific evidence, and even explaining the CSI effect during their closing arguments. Before the legal system adopts changes to “solve” this problem, it is important to engage in careful empirical assessment of whether, in fact, there is a problem to be solved.

Tom R. Tyler is a University Professor at New York University. He teaches in the Psychology Department and the Law School.

Read the full-length print version of Viewing CSI and the Threshold of Guilt, as published in The Yale Law Journal here.

Preferred Citation: Tom R. Tyler, Is the CSI Effect Good Science?, Yale L.J. (Feb. 2006), http://yalelawjournal.org/forum/is-the-csi-effect-good-science.