There is a chance, admittedly probably not a good one, that my DNA could be in a database associated with a rape or murder. Maybe yours might be as well. When I was in high school, I found a bit of cloth in the woods. No idea where it came from. But it got used to clean up after some coital fun and then discarded (I think in a parking garage?). Who knows where it eventually landed and whether it was taken as concrete physical evidence of my involvement in something? If only not being found guilty of things was as easy as not hurting anyone...