In-Depth Study on the CSI Effect

Last night's tip, discussed the CSI Effect. A British study, Lisa L. Smith and Ray Bull, Identifying and measuring juror pre-trial bias for forensic evidence: development and validation of the Forensic Evidence Evaluation Bias Scale, 18 Psychology, Crime & Law 797 (2012), available at: , reviewed how the CSI Effect can lead to pretrial bias. The study incorporated questions about forensic science into the Juror Bias Scale which uses 17 factors to measure juror bias in favor of the defense or the prosecution.

Smith and Bull note that a forensic consultant for the CSI television program estimated that 40% of the techniques portrayed on the show do not exist. They cite other studies which show that viewers of CSI are not more likely to vote to acquit because of a lack of forensic evidence. "Some courts (particularly in the United States) have reported the use of voir dire questions aimed at excluding potential jurors who might be biased in their interpretations of forensic evidence (Thomas,2006). As a result of the unsubstantiated claims of a direct CSI Effect, these questions are often as simple as ‘do you watch CSI?’, yet previous empirical research would predict that such questions are not effective at predicting juror bias." Id. at 16.

Their own study involved 219 people who completed a questionnaire on attitudes towards forensic science and other areas of potential juror bias. The participants used the Likert scale:

  1. Strongly disagree

  2. Disagree

  3. Neither agree nor disagree

  4. Agree

  5. Strongly agree

. . . to indicate how much they agreed with different assertions about forensic science.

The mean scores shown in this table indicate that the group of participants did not have opinions one might associate with the CSI effect.

Smith and Bull conducted another study in which participants were asked to review testimony by four different witnesses. Participants were asked to give their opinion about the usefulness of each type of evidence on a scale from 1 (irrelevant/useless) to 5 (conclusive/definite).

They reached the conclusion that, "participants who demonstrated a higher level of pro-prosecution forensic evidence bias perceived weak DNA evidence to be of higher probative value in this murder trial scenario." Id.