A front-page article in the September 5 edition of The New York Times describes the problem created by stretching the limits of DNA amplification technology without careful validation of the protocol and supporting software.
The location was the DNA lab of the New York City chief medical examiner. A DNA test was used to establish the presence of suspects at a crime scene or match a weapon to an individual. The test used PCR amplification for 31 cycles rather than the accepted 28—this increased the detection sensitivity by 23 or eight times, but also increased the background. Then a software program called the Forensic Statistical Tool, which was developed by two staff members, interpreted it. The tool was not rigorously validated, but was used as a black box. Worse, it was withheld from critical evaluation and review.
The conclusion of the two-page documentary quoted attorney Donna Aldea: “This case is a poster child for how ‘DNA evidence’ can literally be fabricated out of thin air, and how statistics can be manipulated to create a false impression of ‘scientific evidence’ of guilt.” To read about the case, click here.
This is but one more example of the need for a critical review of all forensic science.
Robert L. Stevenson, Ph.D., is Editor Emeritus, American Laboratory/Labcompare; e-mail: [email protected]
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