CSI Effect

The CSI effect refers to the belief that jurors’ expectations about forensic evidence at trial are changing due to the popularity of crime investigation programming such as CBS’s CSI: Crime Scene Investigation. Much of the support for this effect comes from anecdotal evidence. The limited empirical evidence on this topic indicates that CSI may influence some of jurors’ case perceptions but has no effect on verdict decisions.

CSI is one of the most popular shows on network television, consistently ranking high in the Nielsen ratings and spawning several spin-off shows. These shows depict crime scene investigators using highly technical procedures to recover microscopic evidence that ultimately reveals the details of the crime, including the perpetrator. Criminal investigations in real life differ markedly from this representation. In actuality, forensic evidence such as DNA and fingerprints are not always available from a crime scene, and when they are available, they may only be analyzed in important cases or in larger departments due to the expense. Furthermore, forensic laboratories may take weeks to return results that are less than conclusive. According to attorneys and the media, inaccurate portrayals put forth by programs such as CSI are causing jurors to expect more, and stronger, forensic evidence at trial. The concern is that when prosecutors fail to present this evidence, jurors are being more lenient, providing fewer convictions.

Belief in the CSI effect is pervasive among the legal and media communities. According to news reports, evidence of the CSI effect has been found in courtrooms around the country. For instance, in Phoenix, Arizona, jurors in a murder trial voiced concern that a bloody coat introduced as evidence had not been tested for DNA, even though tests were not considered necessary because the defendant had admitted being at the murder scene. Some observers have attributed the 2005 acquittal of actor Robert Blake, charged with murdering his wife, Bonnie Bakley, to the CSI effect. Even though the prosecutor presented more than 70 witnesses against Blake in this case, it is believed that the jury wanted to see forensic evidence such as blood splatter or gunpowder residue and found Blake not guilty when such evidence was not presented. Attorneys have even begun questioning potential jurors about their viewing habits during voir dire and warning jurors about the fictional nature of CSI.

The CSI effect is most commonly defined as leading to a prodefense bias, as the above examples illustrate. In this sense, exposure to crime investigation programming serves to raise jurors’ conviction threshold, requiring more incriminating evidence to find guilt. However, this effect can also be conceptualized in another way. Some commentators note that crime investigation programming enforces the belief that forensic science is infallible and can provide definitive evidence of guilt. Adherence to this belief would actually work for the prosecution, leading to more convictions when any type of forensic evidence is presented, regardless of quality. In this way, crime investigation programming may actually lower jurors’ conviction threshold, requiring less incriminating evidence to find guilt.

To date, little empirical research has examined the impact of crime investigation programming on jurors’ verdicts and case perceptions. The little research that does exist, consisting of a few law reviews and conference presentations, typically examines this effect by measuring mock jurors’ exposure to crime investigative programming (e.g., hours per week) and having them read through a case summary and answer various questions about the case, including verdict.

The results of these preliminary studies are mixed, but most suggest that watching crime investigation programming does not influence verdict. In three studies, mock jurors who report watching CSI a lot were no less (or more) likely to find a defendant guilty than are mock jurors who watch little or no CSI. However, one study did find the predicted prodefense effect, such that more hours of TV watching was related to a perception of less strength in the prosecution’s case, which was related to more acquittals. Also, most studies have found that the more a mock juror finds the shows to be believable and realistic, the more likely the juror is to favor the prosecution and find the defendant guilty. Thus, whether jurors believe the shows are realistic may be a better predictor of decisions than how much the juror watches the shows. Finally, there is also some suggestion that prosecution’s warning against CSI-caliber evidence may produce a backfire effect, weakening the prosecution’s case among jurors who do not watch CSI.

Why is there no direct relationship between CSI and verdict? Intuitively, it seems like such programming should have an effect on jurors’ expectations for evidence. There is a large body of research identifying the media as an important source of knowledge and expectations, particularly for events for which people have little experience, such as a trial. Should a relationship between exposure to criminal investigation programming and juror behavior truly exist, there are a variety of possible reasons a clear effect has not emerged in research. As already noted, there are at least two possible effects viewing CSI can have on juror behavior: It can make jurors expect high-quality forensic evidence and therefore raise the conviction threshold, or it can lead jurors to believe that all forensic evidence is infallible, thereby lowering the conviction threshold when forensic evidence is present. It is plausible that both effects may be occurring simultaneously, such that jurors are coming to require forensic evidence at trial but at the same time are finding any forensic evidence sufficient for guilt. These two effects may therefore be working against each other, leading to no noticeable change in verdict.

Another possibility is that CSI programming may only influence the behavior of certain types of people. It has been suggested by Tom Tyler that the overvaluing of forensic evidence caused by exposure to CSI may be strengthened among those greatly in need of closure or belief in a just world. Similarly, jurors who do not have much need for cognition may be more likely to rely on expectations generated by crime investigation programming as a cognitive heuristic.

In conclusion, empirical research has yet to identify a clear CSI effect, at least as conceptualized by the legal community and the media. Research efforts continue in an attempt to ascertain what influence, if any, such programming has on juror expectations and behavior.


  • Tyler, T. R. (2006). Viewing CSI and the threshold of guilt: Managing truth and justice in reality and fiction. Yale Law Journal, 115, 1050-1085.

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