After all, isn't this the first thing an "expert of autopsy" should find out?
9/10 times this is revealed to you (because of the way the game is setup). However, I want to play "Classic Night" mode (method of death is not revealed) in one of my custom setups with a Coroner who will be able to determine how a person was killed. I had Coroner in there to begin with but removed him when I found out that he can't determine how a person died.
When the Coroner investigates the target, they should find out the method of death (throat slit, riddled by bullets, high-caliber gun, duel/shootout, etc).