Johnny Depp Subpoenaed in Murder Case

Johnny Depp has been dragged into a bizarre criminal case by a lawyer who wants to prove his client is insane.

Depp was served with legal docs at his premiere Thursday in Hollywood (above) for his movie, "Transcendence." And here's why.

Nancy Lekon was driving a limo in downtown L.A.'s Skid Row neighborhood back in 2009 and allegedly mowed down a pedestrian, dragging her for a mile and killing her.

Lekon has been charged with murder and will stand trial later this month. She pled not guilty by reason of insanity.

As for how her public defender plans to prove she was insane at the time of the killing ... enter Johnny Depp.

Lekon told officers at the time of her arrest she was in a relationship with Johnny Depp and was in the area so they could rendezvous.

The public defender now wants to call Johnny to the stand, to show the jury she's delusional.