Forensic science — the kind that traces the grooves in bullets, the mark of a shoe, or the scrape of a tool — emerged in the early 20th century as a way to professionalize police work. But once its findings made their way into the court system, it became almost impossible to divide the good forensic science from the bad.

In an in-depth feature for The Nation, Meehan Christ and Tim Requarth look at the case of Jimmy Genrich, who was found guilty of a series of pipe bombings in the early 1990s after forensic evidence linked tools found in his apartment with markings on the bombs.

The evidence was circumstantial — Genrich was nowhere near the scene of the crime — and while the forensics specialist was able to show that the tools Genrich had in his possession could have made the marks, he was unable to show that similar tools would make the same marks. “Holy shit, this is not science,” remembers Genrich’s lawyer. “It’s like voodoo.”

Law enforcement borrowed terms from science, establishing crime “laboratories” staffed by forensic “scientists” who announced “theories” cloaked in their own specialized jargon. But forensic “science” focused on inventing clever ways to solve cases and win convictions; it was never about forming theories and testing them according to basic scientific standards. By adopting the trappings of science, the forensic disciplines co-opted its authority while abandoning its methods. Once a technique has made it into court and survived appeals, subsequent judges, most of whom have no scientific training and little ability to assess the scientific validity of a technique, will continue to allow it by citing precedent. Forensic examiners, in turn, cite precedent in order to claim that their techniques are reliable science. Prosecutors point to guilty verdicts as evidence that the science brought to court was sound. In this circular way, legal rulings — which never really vetted the science to begin with — substitute for scientific proof … Nowhere in this process is anyone required to provide empirical evidence that the techniques work as advertised.

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