This is how I see it.
And, although a jury can do anything (and often does), I don't see that the Laundries did anything different from what any other parents would do.
I think both families have suffered immensely, but I don't think the Laundries are liable for behaving in a way that might or might not have made the Petitos feel better. They had to do what was right for their family and their situation at the time.
Sharing their thoughts that Gabby *might* be dead would have been perceived as cruel to my way of thinking. Unless I knew for sure someone was dead, I would not suggest that to their loved ones.
The Laundries were probably trying to give their son the benefit of the doubt--he was likely very upset and they seemed to sense he might commit suicide, so why would they exacerbate his angst? I see Brian as being a person who was high-strung, and his parents were probably used to trying to calm him down. Just all MOO, of course, but the last thing a parent would do would be to suggest to the other set of parents that their child might be dead.
None of us can say for sure what we would have done in the Laundrie's position, but I think I would have held out hope that Gabby was alive, maybe she had run off and was mad, maybe they had a fight and he hit her, maybe many things. But the last thing I'd do is run to her parents and tell them I thought she might be dead when I didn't know for sure.
I don't think Brian confessed to them. I think he left them hanging and that's why he wrote the suicide note he did.
There would be no reason to write that note if he had confessed to his parents. They were the only ones left he cared about and he wanted to soften the blow. He made up an odd tale, but I think he did it to ease the pain his actions would cause for his parents.
All MOO.