Crimes, Courts, and Cops

A lawyer's perspective on the pursuit of justice.

Misplaced Faith In Expert Witnesses?

Have we trusted expert witnesses too much in criminal trials?

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).

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The problem, though, is that for years courts have been led to believe that disciplines such as fingerprinting, handwriting analysis and ballistics are as accurate and reliable as DNA analysis and have allowed experts to testify accordingly. Who knows how great an impact such unwarranted certainty has had?

Among other concerns, the Committee also found great disparities among forensic laboratories at the state and federal level regarding funding, training, certification and even the availability of analytical instruments. The Committee made a variety of wide-ranging recommendations, including funding more basic research in forensic sciences and establishing a National Institute of Forensic Sciences to develop and enforce "best practices" for forensic scientists and laboratories.

We can hope that the Committee report will lead to improvements in the future, but that still leaves our criminal justice system with an uncomfortable past and present.

Jim Silver, J.D., is a criminal defense attorney and former prosecutor.

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