Anesthesiologist Dr. Steven Shafer is spending his fourth day on the witness stand today (21.10.11) in the trial of the late singer's personal physician Dr. Conrad Murray, whohas been charged with involuntary manslaughter of the pop star after he was accused of giving the 'Thriller' hitmaker an overdose of Propofol while trying to help him sleep.
When asked whether Michael could have caused his own death by removing a clamp on an intravenous line of Propofol, Shafer replied: "That's a possibility."
But the medical expert said that hasn't changed his opinion that Murray was culpable in the singer's death.
Coroner's officials have determined the singer died from acute Propofol intoxication and also noted there was anti-anxiety drug lorazepam in Michael's system in June 2009.
Shafer explained there is no way to determine whether Murray or the singer were responsible for starting the flow of the drug that dripped into Michael's veins.
Murray's lawyers claim Michael woke up when the physician left the room and gave himself the drug, but Shafer said this possible outcome was "in no way exculpatory" because Murray would've had to set up the procedure.
Defense lawyer Ed Chernoff began cross-examining Shafer by attacking the conclusions he has reached in court during his testimony.
Chernoff said to him: "You understand that everything you said in the last three days was your opinion."
And Shafer replied: "I stated my name, which I think was a matter of fact."
The defense lawyers are expected to bring forward Murray's case following Shafer's testimony.
Murray - who denies involuntary manslaughter - faces up to four years in prison if he is found guilty.