A criminal jury’s expectations of the quality of forensic evidence has changed greatly due to a juror phenomenon known as the “CSI effect.” This phenomenon is named after the popular police television series “CSI: Crime Scene Investigation,” which depicts forensic science as the magical key to solving grisly crimes. Jurors who watch these shows may erroneously believe that they have great knowledge and insight about the use of this evidence, even when their understanding of forensic evidence is based on fictional crime scene technicians and the evidence they can get in their cases.
Most criminal attorneys know it’s unrealistic to believe that forensic evidence is always present at a crime scene, that lab testing is quick, that cost is never a factor, and that forensic results are always decisive and accurate. Unfortunately, the CSI effect surfaces during jury deliberations despite court admonitions and attorneys’ pleas. This means that both sides should be concerned about the CSI effect and should address this phenomenon from the start of a trial, i.e., during voir dire, and while introducing evidence, by
- Discussing with potential jurors their possible misconceptions about forensic evidence by asking what television programs they watch.
- Using the jurors who are CSI viewers as a platform to discuss the limitations of scientific evidence, if you plan to present scientific evidence in your case-in-chief, and then excuse jurors who seem to expect more scientific evidence than will be introduced at trial.
- Identifying jurors who are skeptical of this type of evidence, if you are opposing the forensic evidence, as well as those who appear open to alternative theories or experts that the defense plans to present.
- Introducing “negative evidence” that explains, for example, why fingerprints were not present on an item of evidence, or emphasizing the absence or inadequacy of evidence and asking for jury instructions when applicable, especially if negative inferences may be permitted.
There are certainly those who discount any CSI effect, but it is probably better to be safe than to potentially lose a case because of the jurors unrealistic expectations.
For more on introducing scientific evidence at trial, see Scientific Evidence and Expert Testimony in California.
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