. >> 2007, stacy castor contacts a defense attorney, chuck keller. >> i grabbed my investigator, gabe very thorough. >> he goes to work and never stops defending stacey. >> we have photographs, forensics, toxicology reports, fingerprints, the dna. >> ashley wallace's fingerprints are nowhere to be seen on any of the items tested. and whoever killed david had to have handled these items. >> this was a prosecutor who loves forensic's evidence a dream. because it had computer evidence. it had dna evidence. it had forensic linguistic analysis, which is you know, who wrote the note? plus, she's a pretty -- pretty rotten human being. i wanted to make sure she was convicted. >> so, we had been given this remarkable access to both d.a. fitzpatrick and his team and to chuck keller and the team working with him to try to defend stacey castor. and remember, for this defense team and this young defense attorney, what he has to do is come up with reasonable doubt. he really just needs one juror to think that it's possible that ashley could have done this. >> we were looking for evidence of the acc