mixture that was consistent with a combination of diane holik and russo. reporter: was it enough to say for sure, though no. reporter: because dna no, we can t exclude him. it s consistent with him. but it s not the kind of dna that you can eliminate the rest of the world. reporter: right. just really increased suspicion is all. yes. it was helpful. it was not dispositive. reporter: and the hairs found on that wet towel left on diane s couch? we sent the hair off to a lab, and they did a mitochondrial dna test on the hair, and again we could not exclude mr. russo. reporter: you couldn t say for sure it was him. couldn t say for sure, no. reporter: so close, just not quite the absolute proof they d been hoping for. but the dna did provide one very helpful service. police had confirmed the alibis of diane s fiance dennis and her ibm friend ray, these tests