An expert defense witness suggested on Monday that Michael Jackson could have risen from his bed, picked up a syringe left by his doctor and given himself a fatal dose of a powerful anesthetic in 2009.

But the testimony by Dr. Paul White in the trial of Dr. Conrad Murray was ridiculed by prosecutors in an aggressive cross-examination of the key witness for the defense.

As the trial, now in its sixth week, began drawing to a close, Murray told the judge he was still considering testifying in his own defense, despite previous assurances by his lawyers that they did not plan to call him.

I have not made a decision, Murray said. ... It depends on how the case progresses.

In a damaging day for Murray, who has pleaded not guilty to the involuntary manslaughter of Jackson, White was forced to acknowledge he would never agree to give propofol to a patient in a bedroom to treat insomnia, as Murray has admitted doing.

Propofol, normally used to sedate patients before surgery, was ruled the chief cause of Jackson's death.

It's something that no amount of money would convince me to accept or take on as a responsibility, White said.

Administering propofol for insomnia is an off-label use of the drug that had not been studied, White said.

White, an expert on propofol, said that after Murray gave Jackson a relatively small dose of 25 milligrams of the drug, he might have walked out of the room and left a syringe with another 25 milligrams of the agent that Jackson called his milk. Neither side in the case has said where a syringe might have been located.

Murray's attorneys have argued during the trial that Jackson may have self-administered propofol, but they have until now provided few details.

But an incredulous prosecutor cited prior testimony about how Jackson was lying in bed on June 25, 2009, wearing a urine-collecting device called a condom catheter and having taken several sedatives.

And so Michael Jackson is walking around, wheeling an IV stand, attached to a condom catheter and Conrad Murray is somewhere else on the phone? prosecutor David Walgren asked White. It's a possible scenario, White responded.

LEAVING JACKSON'S BEDSIDE

The singer might have self-injected through a port on an IV line that Murray had installed for him, White said.

Prosecution witnesses have presented a scenario under which Murray placed Jackson on an intravenous drip of propofol after the initial injection, as he had done in about two months of prior nightly propofol treatments.

Prosecution witnesses have testified Murray was not properly monitoring Jackson, in a bid to bolster the charge of involuntary manslaughter, or gross negligence, against him.

White himself admitted that he would have not left Jackson's bedside since, as Walgren said, the singer had confessed he liked to push the propofol into himself.

White also told the court that he had been paid over $11,000 for his testimony by the defense team.

Murray faces up to four years in prison if convicted. Defense attorneys said they will call a researcher on Tuesday who prepared mathematical models White used to analyze the case, and that she would be their final witness.

Prosecutors said they plan to call back their propofol expert, Dr. Steven Shafer, to rebut defense testimony before both sides make closing arguments and hand the case to the jury.