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Monday, July 27, 2009

But criminal forensics has a deeper problem of basic validity. Bite marks, blood-splatter patterns, ballistics, and hair, fiber and handwriting analysis sound compelling in the courtroom, but much of the “science” behind forensic science rests on surprisingly shaky foundations. Many well-established forms of evidence are the product of highly subjective analysis by people with minimal credentials—according to the American Society of Crime Laboratory Directors, no advanced degree is required for a career in forensics. And even the most experienced and respected professionals can come to inaccurate conclusions, because the body of research behind the majority of the forensic sciences is incomplete, and the established methodologies are often inexact. “There is no scientific foundation for it,” says Arizona State University law professor Michael Saks. “As you begin to unpack it you find it’s a lot of loosey-goosey stuff.”
Forensic "science": Popular Mechanics explores the uneasy history of forensic science, developed (as the article's subhead puts it) "not developed by scientists" but by "cops who were guided by little more than common sense." Some truly eye-opening anecdotes here:
A 2006 study by the University of Southampton in England asked six veteran fingerprint examiners to study prints taken from actual criminal cases. The experts were not told that they had previously examined the same prints. The researchers’ goal was to determine if contextual information—for example, some prints included a notation that the suspect had already confessed—would affect the results. But the experiment revealed a far more serious problem: The analyses of fingerprint examiners were often inconsistent regardless of context. Only two of the six experts reached the same conclusions on second examination as they had on the first.

Ballistics has similar flaws. A subsection of tool-mark analysis, ballistics matching is predicated on the theory that when a bullet is fired, unique marks are left on the slug by the barrel of the gun. Consequently, two bullets fired from the same gun should bear the identical marks. Yet there are no accepted standards for what constitutes a match between bullets. Juries are left to trust expert witnesses. “‘I know it when I see it’ is often an acceptable response,” says Adina Schwartz, a law professor and ballistics expert with the John Jay College of Criminal Justice.
Via MeFi, where commenters like Optimus Chyme point out the problems go much deeper:
I'm an avid reader of criminology textbooks; the best/most interesting book in my little collection is probably "Practical Homicide Investigation," 3rd edition. It is extremely detailed and well-researched and much beloved in the field.

And it has a chapter about psychics.

Not "this is bullshit and you should ignore it." A whole chapter that says, more or less "if you are really stuck, you might want to consult with a psychic." This is in the definitive homicide investigation handbook for professional law enforcement.

So, uh, no: I'm not very surprised by this.