When a character is murdered, their reincarnation/child/successor should be able to let the ghost of the deceased haunt their murderer. The haunting would cause various nuisances to the haunted (i.e. making the character spontaneously crawl, turning some FEPs black, dropping inventory objects at random, etc.) but would otherwise pose no direct or immediate threat to anyone. A character could be haunted by more than one ghost, and the more ghosts haunting a character, the more often the nuisance events would occur. The haunting would end after the haunted has played for some time in-game or after a special action is performed. Once ended, the ghost would go back to being a normal ancestor for their reincarnation/child/successor and would no longer be able to perform a haunting.
The purpose of this is to cut down on murders which are performed for the fun of the player or other meta-game reasons. If there is a risk the murderer would be inconvenienced in some way after the fact, it would be less likely they would kill another without having some in-game benefit to counter the "cost" of the nuisances.
It's possible this could be exploited (i.e. spam-alt hauntings), so it shouldn't be possible to let an ancestor go on a haunting unless it (or the killed character) meets certain criteria, such as LP, age, etc.
Obviously, the implementation of this is completely dependent upon how the devs implement ancestral worship in general, which is why I'd rather not go into specific mechanics yet.