A 10-second handshake could transfer a person’s DNA to an object that the person never touched.
In handshaking experiments, people who never picked up a knife became the major source of DNA on the handle about 7 percent of the time, forensic scientist Cynthia Cale reported February 21 at the annual meeting of the American Academy of Forensic Sciences. That DNA was transferred to the knife when the person’s handshaking partner grasped the handle.
In a separate study, the last person to touch an object such as a communal pitcher was often not the one who left the most DNA behind, Leann Rizor, a forensic anthropologist who did the work at the University of Indianapolis, reported at the meeting.
The findings suggest that even brief contact with another person or object could spread DNA far and wide, which could complicate crime scene investigations. While the results don’t mean DNA evidence is unreliable, Rizor and Cale said, investigators should be careful to account for these accidental transfers.
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“We can’t discount [the idea],” [forensic geneticist Mechthild Prinz] says, “but we shouldn’t use it to throw the evidence out in every single case.”
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