A new report from the Justice Department all but admits that their laboratories have been making up results in the cliched "hair identification" seen routinely on crime shows, and considered a routine test:
FBI overstated forensic hair matches in nearly all trials before 2000
The Justice Department and FBI have formally acknowledged that nearly every examiner in an elite FBI forensic unit gave flawed testimony in almost all trials in which they offered evidence against criminal defendants over more than a two-decade period before 2000.There are a number of problems with our system of forensic analysis as part of the justice system. However, first, and perhaps foremost, it is wholly under the oversight of one of the two sides of the case, the prosecution. The forensics people are, by a large, told who is the suspect, and what the evidence they are being given is intended to prove. Even honest people who work for other people tend to try to satisfy them; given hairs that look similar, they're likely to conclude they came from the same person. Are all the hairs on your head identical?
Of 28 examiners with the FBI Laboratory’s microscopic hair comparison unit, 26 overstated forensic matches in ways that favored prosecutors in more than 95 percent of the 268 trials reviewed so far, according to the National Association of Criminal Defense Lawyers (NACDL) and the Innocence Project, which are assisting the government with the country’s largest post-conviction review of questioned forensic evidence.
The cases include those of 32 defendants sentenced to death. Of those, 14 have been executed or died in prison, the groups said under an agreement with the government to release results after the review of the first 200 convictions.
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The admissions mark a watershed in one of the country’s largest forensic scandals, highlighting the failure of the nation’s courts for decades to keep bogus scientific information from juries, legal analysts said. The question now, they said, is how state authorities and the courts will respond to findings that confirm long-suspected problems with subjective, pattern-based forensic techniques — like hair and bite-mark comparisons — that have contributed to wrongful convictions in more than one-quarter of 329 DNA-exoneration cases since 1989.
This is where confirmation bias arises. However, this would have been easy to defeat for hair analysis, if the testing had been properly controlled. If, for example the hair examiners had been given samples of 10 similar hairs from different sources, including the subjects. and asked to match them to the crime scene sample, bad examiners would be readily detected, and the error rate well known and established (and thus probably discredited). The same is true for "bite marks".
Certainly, not all those convicted with the help of this evidence were innocent; but you have to wonder if this evidence was less than solid, what other parts of their cases would not hold up to stricter scrutiny.