After the clarification of how haunt works only ever fullclaim if you have enough information for a full scumread or your death is inevitable. So long as we have graverobber its better for an officer to be dead than have his role permanently removed from the game. Incidentally this removes a cheap way to talk yourself out of a lynch.
Claim if you are town that is guaranteed to be lynched and you have anything that helps town more so than mafia, but at that point your lynch is mandatory.