Call it the “CSI effect,” or call it a general willingness to believe that science can give people the answer to anything, but people tend to think that genetic evidence – especially DNA – is absolute.
It’s really not all that simple. DNA evidence can be wrong.
Trace DNA can transfer and travel remarkable lengths
Genetic testing has advanced rather remarkably over the years, especially since about 2000, allowing for evidence to be drawn from smaller and smaller samples. Unfortunately, that also means that it’s even easier for the experts to make a mistake.
Take, for example, a 2012 incident in San Jose, California, where a 25-year-old homeless man was nearly convicted of the home invasion and murder of a millionaire investor.
The homeless man had no memory of the event – or the entire night. He’d actually been in a hospital, being monitored every 15 minutes, at the time due to acute alcohol poisoning. His DNA managed to travel to the crime scene without him, likely on the clothing or shoes of the paramedics who responded to the millionaire’s home. They were the same paramedics who had taken the homeless man to the hospital a few hours earlier.
While high profile, that’s far from the only time such incidents have been recorded. Secondary transfer of DNA has caused genetic evidence to be erroneously linked to numerous violent crimes, including the Amanda Knox trial in Italy.
Don’t let a prosecutor’s claims of genetic evidence drive your decisions
It’s important to remember that the authorities can lie to you, and that includes claiming to have DNA evidence they don’t actually have. However, it’s also important to remember that DNA evidence isn’t nearly as absolute as it has been made to seem.
If you’ve been accused of a violent crime, make sure you have carefully considered all your defense options before you make any decisions.