“The close association between forensics and law enforcement is particularly controversial. According…”
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The close association between forensics and law enforcement is particularly controversial. According to Frederic Whitehurst, a chemist and former FBI investigator, forensic scientists can “run into a sledgehammer” when they contradict prosecutors’ theories. “What we seem to know in the world of science is that there are some real problems in the world of forensic science,” Whitehurst told a reporter from the journal Nature. “We’d rather work on something cleaner.” It is easy to see why a chemist might consider forensics “unclean”; criminal investigations regularly flout scientific safeguards against bias. Analysts often know the identity of the suspect, potentially biasing results in favor of police’s suspicions. Even more concerning, some crime labs are paid not by the case but by the conviction, creating a strong incentive to produce incriminating evidence.
Whitehurst’s comments echoed a major report in 2009 by the National Academy of Sciences (NAS), which painted a damning portrait of forensic practices. “Many forensic tests—such as those used to infer the source of tool marks or bite marks—have never been exposed to stringent scientific scrutiny,” the report concluded.
One serious problem with those tests is that they allow for high levels of subjectivity. The NAS authors wrote that fingerprint analysis, for example, is “deliberately” left to human interpretation, so that “the outcome of a friction ridge analysis is not necessarily repeatable from examiner to examiner.” I saw this up close while working at the public defender’s office in New Orleans. Explaining his procedure for determining a match, a fingerprint examiner said in court that he would look at one, look at the other, and see if they match. When asked how he knew the two prints definitely matched, the examiner merely repeated himself. That very logic leads the FBI to claim fingerprint matches are “100 percent accurate.” Of course they are, if the question of a match is settled entirely by the examiner’s opinion. Without any external standard against which to check the results, the examiner can never be wrong.
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– Forensic Pseudoscience | Boston Review (via dendroica)
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