Forensic scientists who testify for criminal defendants are under fire. They ought to be praised.Last month, the National Academy of Sciences (NAS) released a wide-ranging report expressing alarm at the way forensic science is used in the courtroom. Among the many problems the report addressed was the tendency of many states to see state-employed forensic experts not as independent scientists, but as part of the prosecution's "team." The problem with that sort of arrangement is obvious: It introduces pressure—subtle or overt—on scientists to produce results that please police and prosecutors. The NAS report recommends that state-employed forensic experts be neutral....