actually play in identifying this man? cnn's alexandra field visits an evidence lab to learn how authorities were able to find wint with a pizza. >> reporter: it's potentially the smoking gun, a pizza box found at the scene. inside crust that investigators say connects daron wint to a heinous crime. this is a good find for an investigator. >> exactly, yeah. >> reporter: dr. david zang runs a dna identification lab in new york city. he says a single bite mark can be enough to crack a case. >> swab the pizza to get as much dna from the crust as we can. >> reporter: he says investigators also likely tested a crumb. >> put it in the tube. get the cells out and proceed to the dna extraction. >> reporter: first, a machine separates out the dna. >> purifying the dna. >> reporter: then the sample is amplified. millions of copies are made that make the sample large enough to