Genetic evidence, in the form of DNA, is increasingly being used in all manner of police investigations, from homicides to sex crimes. Thanks to shows like “Law & Order” and “CSI,” people tend to think that DNA evidence is infallible.
That’s not exactly true. In fact, as the science surrounding DNA evolves, it’s entirely possible that innocent people are going to end up convicted of crimes based on questionable evidence thanks to something known as “touch-transfer DNA.”
Less and less genetic evidence is needed for testing — and that’s a problem
In the early days of DNA testing, it took a significant amount of genetic material for any kind of forensic analysis. These days, it takes hardly more than a few skin cells from a crime scene – things virtually invisible to the naked eye – to obtain someone’s genetic profile.
Here’s the issue: Humans are constantly shedding skin cells, hair and bodily fluids, and those pieces of genetic material can get passed from hand to hand and object to object very easily. DNA can end up traveling miles from its original source.
Take, for example, the case of the homeless man who was nearly sentenced to death row for allegedly killing a millionaire in a home invasion based on tiny amounts of his DNA found at the crime scene. The homeless man, who had a major drinking problem, admitted that his blackouts were so severe he might have been guilty.
The only thing that saved him was proof that he was actually miles away, recovering from alcohol poisoning in a hospital bed at the time of the murder. He’s was brought there by the same paramedics who later responded to the homicide, and they carried small traces of his DNA on their clothes and equipment with them, contaminating the crime scene.
There are numerous reasons that genetic evidence can be called into question in court, and touch-transfer issues are just one of them. Don’t let a prosecutor convince you that your case is hopeless simply because your DNA was found on a victim.