While DNA is left behind, I have yet to see a waitress run to the back with a sample, and run it through DNA marker identification. This also assumes it's a cl

While DNA is left behind, I have yet to see a waitress run to the back with a sample, and run it through DNA marker identification. This also assumes it's a clean sample and not contaminated with all the other DNA present, simple dust, residue on the surface of whatever the DNA was pulled from and/or whatever. I'm not saying it's not possible, I'm saying that it's very, very, very unlikely, at least for mortals. Source: I worked in 2 labs, one of which did genetic testing. Note: I'm IT, not science, so I was the person that setup the reporting triggers, output, input, etc. I do know something about taking samples and swiping them from a glass isn't the typical way, for many, many reasons.