Forensic science isn’t nearly as straightforward and foolproof as it seems on television crime shows like “CSI: Crime Scene Investigation.” Unfortunately, many jurors may not know that. Are they expecting results like those produced on the show? Can they disregard their crime show biases?
Two law professors recently looked into whether the so-called “CSI effect” is real. How much scientific flair are the participants in court cases expecting? Are they disappointed when the forensic evidence they see is boringly inconclusive?
Many common forensic techniques are far from foolproof, after all. As we’ve discussed before on this blog, a seminal 2016 report by the President’s Council of Advisors on Science and Technology found that feature-comparison methods like bitemark analysis, hair analysis and latent fingerprint analysis lack sufficient scientific underpinnings. For example, little research has actually been done to confirm that every set of fingerprints is different.
The report also found that forensic analysts frequently overstate the certainty of their findings when testifying about feature-comparison methods. Only DNA analysis can be used to demonstrate a connection between a suspect and a crime scene, and that is only when the process is set up properly and the tests are performed accurately.
The two law professors sent surveys to a group of lawyers and a group of laypeople asking how they viewed this type of evidence. The idea was to discover whether these groups of people are affected by the seeming certainty of scientific evidence as presented by “CSI.”
The lawyers were somewhat skeptical of fingerprint evidence. Most of them characterized this type of evidence as “somewhat-to-very reliable,” with over 30% characterizing it as “somewhat-to-very unreliable.”
The general public was much less skeptical. 97% of the lay survey respondents reported holding the belief that fingerprints are always unique.
Interestingly, the general public was more skeptical of DNA evidence as being unique to each individual. Only 91.57% thought so.
The lawyers were even more skeptical. Only 78.4% of attorneys surveyed thought DNA was unique to each individual.
In both cases, the lawyers were asked to gauge what the laypeople were likely to think. Each time, the attorneys estimated that the laypeople would be less skeptical than the lay survey respondents actually were.
That said, most jurors do enter the courtroom believing that DNA and fingerprints yield results that are at least somewhat reliable and possibly nearly infallible.
What will this mean when the time comes to challenge the validity of one of these scientific tests?