Last time I'm responding because this is all hypothetical crap and no one knows exactly what they'd do when presented with such a situation. Hypothetically, I'd be inclined to believe whatever story my child concocted. I wouldn't exactly be some neutral, unbiased listener. Thus, I'd be predisposed to accept whatever defense the could come up with it unless there was ample proof to contradict them. In any case, I'd likely tell them to turn themselves into the police but if they didn't I wouldn't turn them in, I'd simply tell them to leave. If they actually admitted to murdering a missing person and told me where the body was, I'd likely give them a few days head start before telling the family. After that, it's up to the police to apprehend them, I want no part in it nor would I answer my child's calls after that. But again, it's all hypothetical and hopefully will only ever remain hypothetical. If you raised a murderer then you fucked up somewhere.