Last week, The Washington Post revealed that in 268 trials dating back to 1972, 26 out of 28 examiners within the FBI Laboratory’s microscopic hair comparison unit “overstated forensic matches in a way that favored prosecutors in more than 95 percent” of the cases. These included cases where 14 people have since been either executed or died in prison.
The hair analysis review — the largest-ever post-conviction review of questionable forensic evidence by the FBI — has been ongoing since 2012. The review is a joint effort by the FBI, Innocence Project and the National Association of Criminal Defense Lawyers. The preliminary results announced last week represent just a small percentage of the nearly 3,000 criminal cases in which the FBI hair examiners may have provided analysis. Of the 329 DNA exonerations to date, 74 involved flawed hair evidence analysis.
While these revelations are certainly disturbing — and the implications alarming — the reality is that they represent the tip of the iceberg when it comes to flawed forensics.
In a landmark 2009 report, the National Academy of Sciences concluded that, aside from DNA, there was little, if any, meaningful scientific underpinning to many of the forensic disciplines. “With the exception of nuclear DNA analysis … no forensic method has been rigorously shown to have the capacity to consistently, and with a high degree of certainty, demonstrate a connection between evidence and a specific individual or source,” reads the report.
There is one thing that all troubling forensic techniques have in common: They’re all based on the idea that patterns, or impressions, are unique and can be matched to the thing, or person, who made them. But the validity of this premise has not been subjected to rigorous scientific inquiry. “The forensic science community has had little opportunity to pursue or become proficient in the research that is needed to support what it does,” the NAS report said.
Nonetheless, courts routinely allow forensic practitioners to testify in front of jurors, anointing them “experts” in these pattern-matching fields — together dubbed forensic “sciences” despite the lack of evidence to support that — based only on their individual, practical experience. These witnesses, who are largely presented as learned and unbiased arbiters of truth, can hold great sway with jurors whose expectations are often that real life mimics the television crime lab or police procedural.
But that is not the case, as the first results from the FBI hair evidence review clearly show. And given the conclusions of the NAS report, future results are not likely to improve. What’s more, if other pattern-matching disciplines were subjected to the same scrutiny as hair analysis, there is no reason to think the results would be any better. For some disciplines the results could even be worse.