According to the National Registry of Exonerations, at least 139 people were exonerated of crimes in the U.S. last year. Some 2,100 have been exonerated since 1989, when DNA evidence was first used to exonerate someone. Today, people are being found innocent using a variety of methods that don't always involve DNA, but the principle remains the same: Sometimes, the criminal justice system convicts innocent people.
When a crime scene sample has evidence of more than one individual crime labs attempt to assign the results to particular individuals. When there are DNA alleles from only two people the process is usually straightforward -- there is a "major contributor" and "minor contributor" identified. The problem becomes more complicated if there is evidence of DNA from three or more persons in the mixture. Until recently, many labs reported results as "inconclusive" because separating the mixture of DNA was too subjective. Then several software companies developed algorithms that could assign the DNA profiles to particular individuals by using statistical probabilities. This method of "probablistic genotyping" has been controversial among scientists in the field and forced courts to confront much new evidence.
On July 27, USA TODAY NETWORK-Wisconsin sent an open records request to the Wisconsin Department of Justice. It was seeking reports on the operations of the state crime lab and whether there continue to be backlogs in processing evidence. Hours after the request was filed, Attorney General Brad Schimel announced that he would authorize overtime and create 11 part-time positions to help law enforcement collect DNA samples and other evidence.
There is no debating that forensic science plays an important role in the criminal justice system. One assumes there also would be little debate over the position that, when forensic science is used to convict people of crimes in the United States, that science should be precise and believable.
DNA is widely used as evidence in criminal trials. In Wisconsin and across the country, this DNA evidence can be used in two ways: either to link an individual to a crime, or to prove his or her innocence. While DNA testing can be accurate, there are times when this evidence should be challenged. A man in Wisconsin is currently struggling with this very battle, as he has been accused of a crime that occurred more than 20 years ago. It was alleged that in 1989 he sexually assaulted a 12-year-old girl.