Does CSI Effect really lead to more acquittals?

Crime dramas saturate network television. Most focus on science and technology, blending reality and fiction to give viewers unrealistic beliefs about evidence in real-life cases. For the past few years, prosecutors have been lamenting this so-called CSI Effect, stating that jurors are making impossible demands for scientific evidence in order to convict.

But does the expectation of scientific evidence really translate into increased acquittals? And, if so, are viewers of TV crime shows more susceptible to this effect?

Those were the questions that a Michigan judge and two other researchers set out to answer, through a survey of more than 1,000 randomly selected jurors.

Judge Donald Shelton and colleagues found that almost half of the prospective jurors surveyed expected to see scientific evidence in every case, with 22 percent expecting DNA evidence – a highly unrealistic expectation. Not surprisingly, this expectation was stronger for regular viewers of CSI, who were also more likely to believe that their favorite TV crime dramas were realistic.

However, the jurors' expectations did not necessarily translate into an automatic tendency to acquit. Rather, jurors said they would only demand scientific evidence if the prosecutor did not call the victims or others as witnesses. In rape cases, however, CSI viewers were less likely than other jurors to say they would convict a suspect in the absence of DNA evidence (which often is not available in real-life sexual assault cases).

Increased expectations of law enforcement are not necessarily a bad thing, Judge Shelton argued in an essay published in this month’s National Institute of Justice journal (available online here). Perhaps, he wrote, police should make more of an effort to get the scientific evidence that the public seeks. And, when such evidence is not available, attorneys and judges need to learn how to explain this reality to the jury.

"Most importantly," wrote Shelton, who has written extensively on the impact of technology on the law, "prosecutors, defense lawyers, and judges should understand, anticipate, and address the fact that jurors enter the courtroom with a lot of information about the criminal justice system and the availability of scientific evidence."