I don't think it's a coroner, since we have full reveals and no deaths have been covered up by a janitor or anything. Also if the coroner had the ability to see who killed that person it would a) be OP and b)have already given us a mafia member.

Most likely the cop wasted an investigation.

Dropping such obvious hints about being a doc is one of the worst moves ever, what a terrible play. And why the cop would investigate them boggles my mind, another bad play.

With cop and doc play like this we really don't have much of a chance. Hopefully we can get this over with.