Thanks to modern media, everybody seems to know a little about the kinds of forensic evidence that can be used in criminal trials. Most people don’t really question the validity of the science involved – but they should.
Junk science is a big issue in the criminal justice system, and one of the biggest offenders may be fingerprint analysis. Even though fingerprints have been accepted as evidence in courts for more than 100 years, there’s increasing evidence that the science behind the analysis can be deeply flawed.
The illusion of a scientific approach
Here’s the thing about fingerprint analysis: It’s not an exact science. In real-world crime scenes, fingerprints are often incomplete, smudged or somehow degraded. These partial prints are often difficult to analyze and match with a high degree of certainty.
Even the process of matching fingerprints is largely subjective, and personal judgment (or level of skill) can vary greatly from one examiner to another. That often leads to inconsistent results, especially with partial prints, since the whole process lacks standardization between one crime lab and the next. There’s not even a universally accepted threshold for what constitutes a “conclusive” match with partial prints.
Confirmation bias, too, is an issue, when examiners are unconsciously (or consciously) influenced by other evidence or external pressures to see a “match” where none exists.
That won’t stop a forensic examiner from testifying in court, however, that they’ve made a “match” between the fingerprint left at the scene of a violent crime and a defendant. That’s why anybody who is on trial for a serious offense where fingerprint evidence is in use needs an experienced defense who is not afraid to take on a challenge.