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I have read these criticisms before. The article has more on these techniques, and some others.In recent years, legal experts have become deeply concerned about the accuracy of the “friction ridge analysis” central to fingerprint identification. Fingerprints are believed to be unique, but the process of matching prints has no statistically valid model. ... Yet, as University of California–Los Angeles law professor Jennifer Mnookin has written, “fingerprint examiners typically testify in the language of absolute certainty.”
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. ... 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.
FYI.