The sledgehammer in the grave looked pretty clean of any blood, and the only thing mentioned so far being found on it was white paint, I have a hard time believing he used it at the grave site to kill any of them and then cleaned it of blood so well before tossing into the grave.
I'm sure they did fingerprint and dna testing on it, that testimony should be interesting but seems to me had CM's finger prints been found on it, we'd have heard about it by now.
As to the poll a few pages back -
CM killed them all alone, although needed help to get back after dumping the truck near the border, my likeliest suspect for that would be CJ, as she already changed her statement once ('he was home when Joey called on 2/4', then when faced with the cell data - 'I must have been remembering another evening'.
Joey killed separate from Summer and the kids, probably in the afternoon at Chase's storage place, and Chase had Joey's phone as he drove to their home and killed Summer and the kids.
Moo