SPOILER* do not read if you haven't see help me understand what happened

So the killer has the coroner get him off from murdering the coroner's daughter by tampering with her body the whole time thinking it was the original victims body correct?


I didn't really realize what was going on when he tried to pull his daughter out of the tub of roses until it me that her body was not there. So clearly her body was the one he worked on right?

Wouldn't DNA or something of that nature have made it obvious during autopsy that the body was not the same as the head and arms/legs of the victim?

I'm probably about to feel really dumb when someone explains I misinterpreted the ending and if I did can you clarify what happened?

#thinkigetitbutnotsure