cells? >> purifying the dna. >> reporter: the sample is amplified. millions of copies made, make the sample large enough to be seen with the help of a machine. >> the laser with the trace the dna. that's what you are going to see here. >> reporter: a unique readout, dna finger print. to solve the case, that fingerprint can be added to or matched in a federal database including some 14 million different profiles. >> hair. saliva, urine. semen, all these can be used. >> reporter: seemingly small clues picked up at crime scenes. zang says a piece of crust can yield millions of cells or just a few. some times that's just enough to identify a suspect or even solve a case. alexandra field, cnn, new york. >> archbishop romero declared blessed to day. 35 years after his death. romero shot and killed in the