For many years, forensic science has played a prominent role in criminal trials. Experts for both the prosecution and the defense routinely come to court and tell jurors about all kinds of evidence: DNA, drug analysis, fingerprints, writing samples, tool-marks, bite marks, hair samples and many others. That makes sense, doesn't it? We live in an age of reason, and these experts are scientists (or technicians trained in the scientific method) who run the appropriate tests and draw conclusions supported by their findings. Who could argue with that?

Well, the National Academy of Sciences, for one. In 2005, Congress authorized the National Academy of Sciences to conduct a study of the state of forensic science. In 2009, after more than two years of work, an NAS Committee issued its report, Strengthening Forensic Science in the United States: A Path Forward. Some of the conclusions reached by the Committee are troubling.

While acknowledging that forensic science is often invaluable in successfully prosecuting the guilty and exonerating the innocent, the Committee also found that imprecise or exaggerated expert testimony has contributed to the admission of erroneous or misleading evidence. The Committee concluded that there simply are not enough peer-reviewed, published research studies to establish the scientific basis for many of the forensic methods used in trials, particularly those relying on expert interpretation, and that "with the exception of nuclear DNA analysis, . . . no forensic method has been rigorously shown to have the capacity to consistently, and with a high degree of certainty, demonstrate a connection between evidence and a specific individual or source." (NAS Committee Report at 7).