Expert Witnesses

I didn't pay much attention to the recent F.B.I. announcement that testimony by its forensic scientists about hair identification was scientifically indefensible. Then, I learned that the error rate in more than 250 cases reviewed was 96%. These errors resulted in 33 defendants  receiving the death penalty; nine of these 33 have been executed so far.

Eric S. Lander, co-chairman of the President’s Council of Advisors on Science and Technology, has been involved with reviewing expert witness testimony for a number of years. He has a devastating op-ed in today's NY Times. The problem with experts is not only testing of hair. One fellow spent 30 years in prison based on ballistics evidence which proved to be faulty. Another case involved people being convicted of murder on the basis of their teeth marks which subsequently were proved to be tooth marks of insects and crawfish.

Lander cites a 2009 report by the National Research Council, which found that apart from DNA testing, no forensic method had been rigorously shown to consistently and reliably demonstrate a connection between evidence and a specific person.

Lander concludes:

No expert should be permitted to testify without showing three things: a public database of patterns from many representative samples; precise and objective criteria for declaring matches; and peer-reviewed published studies that validate the methods.