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18 June 2009 9:40 AM


Interview with Radley Balko Part IV

My interview with Radley Balko, who is meeting his fans in Denver tonight, began here. Part two is here. And part three is here. The next question:

Q. Perhaps the most significant story you've covered lately involved prosecutors using the services of a bite mark expert, though evidence suggests he is no expert at all. Can you briefly describe that case, reflect more generally on the idea of expert witnesses in our criminal justice system, and explain why you think the status quo is problematic?

In the 1990s, a Mississippi dentist named Michael West became a popular expert witness for prosecutors because he claimed to be a bite mark expert who could find and identify tooth impressions in human skin that no other expert could see. He was eventually exposed as a fraud by 60 Minutes and other media outlets, though he continued to testify in Mississippi, and there are still people in prison who were convicted primarily because of his testimony.

West got on my radar as I've reported on the problems with the forensics system--particularly in Mississippi, where until last year, one doctor who colleagues say is sloppy and disreputable has done 80-90 percent of that state's criminal autopsies for the last 20 years.

That doctor, Steven Hayne, and West were the primary reason two men were convicted of the rape and murder of two little girls in the early 1990s in Mississippi. DNA testing exonerated both men last year. Earlier this year, I wrote about another case in which the two men may have fabricated bite mark evidence in a murder case, and another in which a defense attorney conducted an amusing sting to expose West's charlatanism.

Fraudulent experts like West and Hayne have been able to thrive because of some pretty significant flaws in how forensic evidence is used in the criminal justice system. The main problem is that it's presented as science, but isn't really subject to the sort of rigorous testing and peer review that other fields of science undergo. Bite mark evidence, for example, should never be used in a court room. There's no legitimate scientific literature to back up the idea that you can trace tooth imprints on human skin to a single suspect. But the National Academy of the Sciences warned in a big report earlier this year that even areas of forensics we once thought infallible, such as fingerprint evidence, are subject to error, whether it be malicious misconduct, or less nefarious bias and innocent mistakes. The certainty of DNA testing has exposed the flaws in how we've traditionally dealth with forensic evidence.

Juries tend to put a great deal of faith in witnesses that judges certify as experts. The problem is that judges haven't adequately performed their duty as gatekeeper, both at keeping frauds out of the courtroom and preventing legitimate experts from testifying beyond their expertise or exaggerating the certainty of their conclusions.


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