Back in 1982, a 22-year-old woman was found raped and murdered in her Kansas mobile home.
Twenty years later, a man was convicted of that crime – largely based on DNA evidence.
But now, our Birmingham criminal defense lawyers understand that state supreme court justices there have ruled that the defendant in that case may be granted another DNA test, on the basis that short hairs found on the victim’s body were never tested.
The defendant had raised several arguments with regard to the testing, though this was the only one that the Kansas Supreme Court ruled warranted reconsideration. The other arguments included that there was cross-contamination of male and female samples and that a number of the samples found at the crime scene were not compared against the DNA of the victim’s boyfriend.
Specifrically, he was requesting that DNA foud in the fingernail scrapings, underware and shorthairs be cross-tested against the DNA of the victim’s boyfriend.
Only those short hairs will be retested and cross-tested, and regardless of the results, the case illustrates a larger point: That DNA evidence, while a valuable tool for law enforcement and prosecutors, is not full-proof.
Much can be called into question with regard to methodology of the testing, particularly in cold cases like this where the samples themselves may be significantly erroded over time. This can work to either the advantage or disadvantage of the defendant, depending on the circumstances.
A 2008 study conducted by researchers at the University of California, Irvine’s Department of Criminology, Law & Society asserts that DNA tests are not infallible, despite claims of that made by the National Research Council and prosecutors across the country. Researchers purported that, while often and generally reliable, DNA tests are not infallible, and the assumption, taken as fact, that they are has led to many false convictions.
Some of the examples in which a false match may occur, according to the researchers, include:
Coincidental matches. These are matches between two people who coincidentally happen to share the same DNA profile. This is generally rare, but it depends on the type of test being conducted. And far from being a one-in-a-billion chance, as is sometimes asserted, sometimes the chances are closer to on in 790,000 – a much greater probability. It’s even more enhanced when two suspects are related.
Where this might become a big issue is when law enforcement agencies begin cross-testing decades-old DNA samples to those collected by the millions of individuals arrested or imprisoned each year.
Next you have erroneous matches. This happens not necessarily as a result of a false positive, but as a result of human errors in either the way the test was conducted or in how it was interpreted. Among the first 200 people exonerated by post-conviction DNA, two of those were convicted on the basis of DNA testing errors resuting from a combination of technical problems in the lab as well as careless and/or mistaken interpretation. This may seem like a simple “oops,” but both cases resulted in innocent men spending decades behind bars.
And finally, there is always the possibility of intentional planting of DNA, either by law enforcement or lab technicians. While this might seem relatively rare, consider the recent case out of Massachusetts, where a lab technician is facing criminal charges for intentionally skewing results in favor of prosecutors. In the wake of that case, many current and former lab technicians have come forward to report pressure to return favorable results to prosecutors, with the view that they are seemingly “on the same team.”