The Dangers of DNA Testing

Before you give the police a DNA sample, read an alarming new study of crime laboratories published this summer, the largest study of its kind.

Researchers from the National Institute of Standards and Technology gave the same DNA mixture to about 105 American crime laboratories and three Canadian labs and asked them to compare it with DNA from three suspects from a mock bank robbery.

The first two suspects’ DNA was part of the mixture, and most labs correctly matched their DNA to the evidence. However, 74 labs wrongly said the sample included DNA evidence from the third suspect, an “innocent person” who should have been cleared of the hypothetical felony.

The test results are troubling, especially since errors also occur in actual casework. Just ask Dwayne Jackson of Las Vegas.

When he was 18, he was told that his DNA matched DNA from a home invasion and kidnapping of a woman and her two daughters. He was advised that a jury would most likely believe the DNA, not him. Facing a life sentence at trial, he pleaded guilty to reduced charges in 2003.

Mr. Jackson spent nearly four years in a Nevada prison, until the crime lab realized it had accidentally switched his sample with another suspect’s tube. The lab apologized, and he was released from prison.