Scientific methodology is based on generating hypotheses and testing them to see if they make sense; in laboratories throughout the world, researchers spend at least as much time trying to disprove a theory as they do trying to prove it. Eventually, those ideas that don’t prove false are accepted. But fingerprinting was developed by the police, not by scientists, and it has never been subjected to rigorous analysis —you cannot go to Harvard, Berkeley, or Oxford and talk to the scholar working on fingerprint research. Yet by the early twentieth century, fingerprinting had become so widely accepted in American courts that further research no longer seemed necessary, and none of any significance has been completed.
The discussion of fingerprinting is only the most visible element in a much larger debate about how forensic science fits into the legal system. For years, any sophisticated attorney was certain to call upon expert witnesses to assert whatever might help his ease. And studies have shown that juries are in fact susceptible to the influence of such experts. Until recently, though, there were no guidelines for qualification; nearly anybody could be called an expert, which meant that, unlike other witnesses, the expert could present his "opinion" almost as if it were fact.