While other types of evidence and forensic science are increasingly being challenged as unreliable, DNA analysis is the notable exception. It is usually considered the gold standard in the criminal justice arena, especially in prosecutions of violent crimes and sex offenses. And DNA evidence has been used to both convict and exonerate countless individuals.
While the science of DNA analysis stands up to scrutiny, a DNA match does not automatically convey guilt. This is because the way that DNA is collected and stored is highly important, and tainted evidence can implicate the wrong person. Additionally, a recent study has found that the transfer of DNA is more common than we think, and our DNA can end up on objects we’ve never touched.
According to a recent article in Science News, shaking someone’s hand for as few as 10 seconds can transfer your DNA onto that person. If your handshaking partner then handles an object, your DNA could be transferred to that object.
Things become even more complex when multiple people are touching the same object, such as a communal drink pitcher. In one of the experiments, participants in a simulated party atmosphere were given plastic cups and were invited to pour themselves drinks from the same pitcher. Each participant only handled his or her own cup, but everyone touched the pitcher handle. When tested later, the cups were found to have DNA from other participants on them (though they were never directly touched by the participants).
Studies like this suggest that DNA evidence needs to be carefully presented in context and that the science of DNA transfer needs to be more closely studied. In the meantime, if you’ve been accused of a sex offense or violent crime and DNA evidence is a factor, you should know that the evidence may not be nearly as ironclad as it seems.