why did david shepard go back on his deal and completely burn the prosecution? face to face with the man who murdered joseph sonnier. >> you said that mike dixon was a part of this. >> right. >> why did you tell them that? than dishes? re using multiple cleaners on grease can be expensive, and sometimes ineffective. for better value, tackle grease with dawn ultra. dawn is for more than just dishes. it provides 3x more grease cleaning power per drop, which cuts through tough kitchen messes, pre-treats laundry stains, and even tackles grease build-up on car rims. tackle tough greasy messes around your home, and save money with dawn ultra. brand power. helping you better. ♪ if♪ darling, tell me me, loveall the ways ♪ay ♪ ♪ tell me all the ways ♪ all the ways at the store, or to your door. target run and done. cheddar, jalapeno, and sour cream and onion... the spicy nacho stack. i wish i could stack pringles, but i don't have hands. or a mouth to... cool, play funkytown. (funkytown playing) there's a pringles stack for everyone... sort of. ♪ ♪ ♪ take me to your best

while he is free for now, david shepard is spending the rest of his life behind bars at this maximum security prison in west texas. >> i put myself in a bad position, and i've got no one to blame but myself. >> reporter: shepard claims dr. sonnier's death was an accident. >> things got out of hand. unintentionally. gun fired. >> reporter: did mike dickson ever ask you to kill -- >> no, absolutely not, absolutely not. >> reporter: when the police interrogated you, you said dickson was a part of this. >> right. >> reporter: why did you tell them that? >> i embellished. i thought that's what i had to do. >> reporter: what would you say to them right now if they were watching? >> i'd tell them i'm very sorry. i took your loved one. >> reporter: almost seven years after their father's death. >> i thank the lord f moment we had. >> reporter: dr. sonnier's ildren what w.k in limbo, s wan >> it's heartbreaking, and it's also a challenge to make sure that my son knows what kind of man my father was. >> reporter: for "nightline," ryan smith in new york. >> our thanks to ryan. >>> up next, speci