>> reporter: the gun was sent to the firearms lab as ruvin checked to see if he could prove william woodforkt. but woodfork's dna and fingerprints weren't on the door or anywhere else. you look at the security tape? is he on there anywhere? >> he was never on the security tapes. >> reporter: then the tests came back on the dealer's .380. >> it was not the gun that killed eric. it was the same caliber, but the ammunition was different. so it was just one big coincidence. >> reporter: now eric's dealer wasn't looking as good for the murder. not only was the gun not a match, ruvin was convinced that the dealer was never at eric's apartment. as for denise, the woman who had been eric's girlfriend, investigators interviewed her three times. she was cooperative and allowed them to look at her phone. >> her phone records put her at home the night of the murder. >> reporter: so they eliminated denise as a suspect. and again, ruvin started from scratch. >> you don't just come in to somebody's apartment and murder them while they're sleeping and expect to get away with it. and i felt like this was my