I do hope he will be pressured to tell where she is, well I know he will be, but I hope it works. I think LE has a set of circumstances pointing to her not being alive, but no absolute proof, as surely they would have told the family, and the family is still insisting they are not going to believe she is dead until/unless she is found. So right now, I feel they are going to try to build a case based on a number of things that show she must be dead, but not a "death band" hair, or decomposition, etc.
The chances of this particular type of predator having an accomplice or anyone who is "holding" Sierra, is to me, 0%.
JMO