A ten-second handshake can transfer a person's DNA to nearby objectseven if the person does not touch any of them, recent studies have found.

Speaking at the annual meeting of the American Academy of Forensic Sciences, Forensic expert Cynthia Cale noted that several experiments have shown that the DNA of people who never picked up a knife was detected about 7 percent of the time. That DNA was transferred to the knife when the person’s handshaking partner grasped the handle.

In another study, the DNA of the last person to touch an object was often not detected, 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," Rizor said. "The results demonstrate that DNA can transfer easily in social settings and in unpredictable ways."

In Rizor’s experiment, four students sat around a table and poured beverages from the same pitcher. Other students watching the experiment were free to leave the room, talk and move around to simulate conditions in a restaurant. DNA from students at the table was on the pitcher handle and on each other’s cups, even though that each of them handled his own cup and the pitcher.

Moreover, DNA from other students in the room was also detected although none of them had touched the students or the objects at the table. Their DNA is believed to have spread to the cups and pitcher as they talked, coughed or sneezed.