Forensic evidence under the microscope, changing the way we look at expert analysis

High-profile examples of forensic evidence being less clear-cut than is typically portrayed on “C.S.I.” have littered the headlines in recent years, reported The Christian Science Monitor. Perhaps the most significant is last month’s admission by the FBI that, after reviewing 500 cases that employed microscopic hair analysis, examiners’ testimony contained erroneous statements in at least 90 percent of the cases.
Defendants in at least 32 of those cases received the death penalty, according to the FBI. Nine of those defendants already have been executed, and five died of other causes while on death row.
The review is part of an ongoing, long-term investigation of decades of FBI microscopic hair analysis the agency is conducting in partnership with the Department of Justice, the Innocence Project, and the National Association of Criminal Defense Lawyers. The project launched in July 2013, and last month’s announcement covered the first 500 cases of an estimated 3,000 spanning from the 1970s up to 2000.
Brandon Garrett, a professor at the University of Virginia School of Law, said that forensic disciplines like microscopic hair analysis are, at the most, useful “as a tool to exclude” suspects, not a tool to specifically identify them. But they are rarely treated that way by forensic scientists.
“Analysts often seem to do something more ambitious – identify particular people – and that is more than many of these techniques can currently accomplish,” wrote Professor Garrett in an e-mail.
The subjective nature of forensic science has been public knowledge for some time. A report from the National Academy of Sciences in 2009 found that microscopic hair analysis – along with other juror-trusted forensic techniques like bite-mark, ballistics, and even fingerprint analysis – were unscientific in their methodology.
The trust juries put in forensic evidence is part of the problem, experts say.
Garrett published a study in 2009, which studied the trial transcripts of 156 innocent people convicted of serious crimes who were later exonerated by DNA evidence. The study found that 60 percent of the forensic analysts called by the prosecution provided invalid testimony, “with conclusions misstating empirical data or wholly unsupported by empirical data.”
The study noted “the adversarial [judicial] process largely failed to police this invalid testimony.” Defense attorneys rarely cross-examined these analysts, the study added, and rarely obtained experts of their own. Judges seldom provided relief.
Peter Neufeld, co-founder and co-director of the Innocence Project, says that it shouldn’t be the judge’s responsibility to provide the relief.
“The courts are the wrong place, the wrong venue to get it right,” says Mr. Neufeld, who was a co-author on Garrett’s 2009 study. “Defense lawyers, prosecutors, and even juries by and large, are scientifically illiterate.”
While many lawyers, judges, and juries may not be able to distinguish credible forensic testimony from the erroneous, the weight it can have over the ultimate verdict is immense.
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