i did not kill bob mcclancy. i did not have anything to do with killing bob mcclancy.e died of a drug overdose . >> and that was martha ann's story, every word of it was true, she swore. >> if martha ann believes that her husband, bob mcclancy was murdered, she would say it was chuck kaczmarczyk. he was there when bob mcclancy died, by her his admission. he was the one that took photos of bob and manipulated the scene of the death, whether it was a crime scene or not. >> but the battle of the con artists were just getting started and the prosecutors believed they had a strong case. >> what was the most important piece of evidence, in your view? >> the most important piece of evidence, of course, was the mirandized confession taken from chuck kaczmarczyk. >> and what a dark , devious story of murder chuck was about to tell. >>> coming up-- >> keep it simple, make it look as natural as possible. >> powerful testimony from the star witness and from a reluctant son. >> she looked at me as if she wished i was dead. >>> when "dateline" continues. it's tough to breathe and to