An expert in anesthesiology testified in defense of Michael Jackson’s doctor, saying the pop star may have given himself a fatal dose of drugs and that the prosecution’s theory does not fit the evidence.

Michael Jackson may have caused his own death by taking a large quantity of sedative pills and giving himself an intravenous dose of the powerful anesthetic propofol in the final moments of his life, an expert in anesthesiology testified Friday.

Dr. Paul White told the jury at the manslaughter trial of the pop legend’s personal physician that the most plausible explanation for the drug levels detected in Mr. Jackson’s system after his death is that he swallowed pills and injected himself with propofol when his doctor was out of the room.

Defense Attorney Michael Flanagan asked Dr. White whether he would expect “adverse consequences” if Jackson quickly injected a dose of propofol into himself after already ingesting a significant quantity of lorazepam pills and after having been injected with the sedatives lorazepam and midazolam.

“I believe it could potentially have lethal consequences,” White said.

The testimony came on the 20th day of the trial of Dr. Conrad Murray in the Los Angeles County Courthouse. The Las Vegas cardiologist is accused of administering a fatal dose of propofol while trying to treat Jackson’s chronic insomnia.

Dr. Murray’s lawyers maintain that Jackson gave himself the fatal dose. Murray has pleaded not guilty.

White is believed to be the defense’s last witness. His cross examination is set to begin on Monday. The case could go to the jury later next week.

Murray had been hired for $150,000 a month to serve as Jackson’s physician during a planned series of concerts in London. With rehearsals escalating and the concert fast approaching, Murray was attempting to treat Jackson’s complaints of lack of sleep. For nearly two months the doctor had been administering nightly intravenous doses of propofol in the bedroom of Jackson’s rented mansion.

The anesthetic is not a recognized sleep aid and is usually administered by a trained anesthesiologist in a fully-equipped hospital or clinic. But Murray surrendered to Jackson’s insistence that propofol was the only medicine strong enough to help him sleep.

Murray set up an IV system in Jackson’s bedroom. Medical experts testified that the practice was unheard of and extremely dangerous.

Jackson died on June 25, 2009. An autopsy said the cause of death was “acute propofol intoxication.” Murray was charged with involuntary manslaughter and faces up to four years in prison and loss of his medical license, if convicted.

Dr. White’s suggestion that Jackson self-administered a lethal combination of drugs that killed him stands in sharp contrast to the testimony of the prosecution’s expert, Steven Shafer. The Columbia University professor and research scientist said Jackson most likely died while receiving a continuous infusion of propofol set up by Murray.

Mr. Shafer said Murray set up the propofol drip and then left the room. At some point, Jackson stopped breathing and died, Shafer said, because Murray was not at Jackson’s bedside to open his air way.

Shafer said administration of propofol requires an array of resuscitative equipment, electronic monitoring equipment with alarms, and constant vigilance by the attending physician.

He said Murray had effectively abandoned his patient.

Defense attorneys are working to counter Shafer’s testimony and trying to raise doubts in the minds of the jurors about how Jackson died.

White said Shafer’s theory of the propofol drip did not fit with evidence recovered in Jackson’s bedroom. And he said Shafer’s theory that Murray gave Jackson a series of injections of the sedative lorazepam does not fit with drug concentrations found during the autopsy.

White testified that Jackson most likely gave himself a rapid injection of 25 milligrams of propofol between 11:30 a.m. and 12 noon.

He testified that his self-injection scenario better fit the known evidence than Shafer’s offered scenario.

“I cannot understand how it is possible that [Jackson] got a three hour infusion [of propofol] when the evidence does not show an infusion set up and the level of drug in the blood is not consistent with” Jackson receiving an entire bottle of propofol, White said.

On Monday, prosecutors are expected to challenge White’s scenario. In addition they are likely to closely question White about whether Murray followed recognized procedures for administration of propofol and whether he took adequate safeguards.

Analysts say prosecutors will likely argue that even if Jackson self-administered the drug, Murray still had a duty as a physician to monitor his patient at all times.