.... yet he is acting like some latter day Brady and Hindley in not revealing what he did with poor April's body.
I wouldn't allow him that option. I would let him go through a Clockwork Orange session every day of his miserable existence until he revealed the exact spot.
After April's body had been recovered I would place a phial and an hypodermic syringe on his bedside table and remind him, every day, that he was never to be let free.