driving the strube family truck. heather's mother-in-law, admitted driving that truck that very day, but she claimed she couldn't be the killer because she had an alibi. a receipt for ice cream from a restaurant an hour away from the murder showed she could not be heather's killer. well, we found the receipt and we looked at it because she was adamant that she couldn't have done it. narrator: joanna did have a motive. she didn't want to share custody of her grandson with heather. but even prosecutors had to admit that a single wig fiber and traces of gunshot residue made for a thin case. so they gambled. they brought in steven strube and showed him their surveillance tape of the shooter recorded at the scene. we began to ask him if it looked like anybody he knew. and he began to really look hard at the video. can you tell? it is apparent from not only what he said, but how he reacted that he recognized his mother. narrator: prodded by detectives, steven agreed to call his mother while they listened in. she didn't act