andrea canning: leanna harris had lost so much-- her child and her life as she had known it. >>> leannaarris had lost so much. her child and her life as she had known it. by the time ross went on trial, leanna had heard all the revelations she could stand, and she had divorced him. if anyone had a reason to hate ross, to be angry at ross, to not get up on that witness stand for ross, it's her. >> right. >> reporter: but yet she did. >> because she believes 100% that it was not intentional. >> reporter: so there she was in court, not condemning ross, but defending him. >> tell these folks a little about cooper. >> cooper was the sweetest little boy. he had so much life in him. he was everything to me. >> reporter: and everything to ross, too, she testified, as the jury watched family videos of father and son. >> what are we looking at there, leanna? >> that's them in our bed. and that's just kind of a little game that they would play. >> reporter: leanna said ross was the kind of dad who always played at the park. >> you do it, go. ♪ >> reporter: and made goofy videos of his son at snack