Law enforcement has long referred to DNA evidence in criminal cases as the “gold standard.” A person's DNA, whether recovered from an object or person, has been used to convict people for many years. But the detection of DNA may not indicate that a defendant had presence or made contact with an object or person.
“Touch DNA” or “touch-transfer DNA” describes a situation where a defendant's DNA is found on an object or person where the accused did not even touch that object or person. Humans shed DNA continuously and shed DNA transfers freely between persons and objects. Merely touching a doorknob can transfer your DNA to that object and your DNA may then transfer to the next person that touches that doorknob. In other words, your DNA would be found on a person that you have never had contact with.
Touch-transfer DNA or touch DNA may result in a situation where a defendant's DNA is found at the scene of a crime, but that defendant has never been at that scene. This questions the reliability of DNA evidence in criminal cases. For too long law enforcement has touted the trustworthiness of DNA evidence, but they fail to take into consideration touch-transfer DNA or touch DNA.
Where there is DNA evidence, it can get complicated and there are a lot of variables to consider. Often it is necessary to employ the services of an expert to help explain DNA evidence to a jury. The importance of understanding the variables of touch-transfer DNA or touch DNA is critical where a defendant is accused of a serious criminal offense based upon such evidence.