These types of problems have led to scandals at dozens of crime labs across the nation, resulting in full or partial closures, reorganizations, investigations or firings at city or county labs in Baltimore; Boston; Chicago; Colorado Springs, Colorado; Dallas; Detroit; Erie County, New York; Houston; Los Angeles; Monroe County, New York; Oklahoma City; San Antonio, Texas; San Diego; San Francisco; San Joaquin County, California; New York City; Nashville, Tennessee; and Tucson, Arizona, as well as at state-run crime labs in Illinois, Montana, Maryland, New Jersey, New York, Oregon, Pennsylvania, Virginia, Washington, North Carolina, West Virginia and Wisconsin, plus the federally-run FBI and U.S. Army crime labs. Forensic “expert” scandals have also been reported in the United Kingdom.It's not that most of the questioned techniques have been invalidated, it's more that expert witnesses overstated their reliability and high error rates were routinely minimized. If, to use an example from last week's Forensic Science Commission Roundtable, the error rate of microscopic hair comparisons runs around 11 percent, courts have historically been too ready to accept expert testimony declaring a forensic "match." They may be right 89% of the time, but used in volume the technique can and has led to false convictions, including DNA exonerations. Most judges and attorneys, PLN showed, don't understand enough about statistics to comprehend, much less judge, error-rate issues.
The origins of such problems include unqualified or incompetent lab workers, personnel using false academic credentials, contamination in labs that cause false test results, employees falsifying test results to “help the prosecution,” and lab examiners committing perjury. Contributing to these problems is a lack of qualification standards and industry-wide training requirements for lab workers.
One might think that such scandals are caused by a few bad apples in the crime lab barrel, which is the spin typically adopted by the labs themselves. That problem could be fixed by hiring qualified personnel, training them properly and providing adequate oversight. But at least the forensic science that underpins crime lab testing is sound and valid, right? In many cases, wrong.
A 2009 report by the National Academy of Sciences, the most prestigious scientific organization in the United States, revealed that much of the “science” used in crime labs lacks any form of peer review or validation – fundamental requirements for sound science. Such questionable forensic methods include long-established and accepted techniques such as fingerprint comparison, hair and fiber analysis, and bullet matching.
The PLN story walks through these topics in great detail. It's a particularly good starting point for those who haven't deeply considered these subjects.