Robin Williams autopsy results are revealed

Reports authenticate that there were no traces of drugs or alcohol in the comedian at his time of death

Joan Rivers — Cause of Death May Remain Mystery … Because NO AUTOPSY

EXCLUSIVE

We may never know exactly what killed Joan Rivers … because a choice was made NOT to do an autopsy … TMZ has learned.

Sources connected to the NYC Medical Examiner tell us … Melissa Rivers was despondent when Joan died and told doctors she did not want an autopsy performed.  According to New York law, doctors will honor such a request…