Dr. Paul White said Jackson injected himself with a dose of propofol after an initial dose by Dr. Conrad Murray wore off. He also calculated that Jackson gave himself another sedative, lorazepam, by taking pills after an infusion of that drug and others by Murray failed to put him to sleep.
That combination of drugs could have had "lethal consequences," the defense team's star scientific witness said Friday.
Murray has pleaded not guilty to involuntary manslaughter.
White showed jurors a series of charts and simulations he created in the past two days to support the defense theory. He also did a courtroom demonstration of how the milky white anesthetic propofol could have entered Jackson's veins in the small dose that Murray claimed he gave the insomniac star.
White said he accepted Murray's statement to police that he administered only 25 milligrams of propofol after a night-long struggle to get Jackson to sleep with infusions of other sedatives.
"How long would that (propofol) have had an effect on Mr. Jackson?" asked defense attorney J. Michael Flanagan.
"If you're talking effect on the central nervous system, 10 to 15 minutes max," White said.
He then said Jackson could have injected himself with another 25 milligrams during the time Murray has said he left the singer's room.
"So you think it was self-injected propofol between 11:30 and 12?" asked Flanagan.
"In my opinion, yes," White said.
The witness, one of the early researchers of the anesthetic, contradicted testimony by Dr. Steven Shafer, his longtime colleague and collaborator. Shafer earlier testified Jackson would have been groggy from all the medications he was administered during the night and could not have given himself the drug in the two minutes Murray said he was gone.
"He can't give himself an injection if he's asleep," Shafer told jurors last week. He called the defense theory of self-administration "crazy."
White's testimony belied no animosity between the two experts, who have worked together for 30 years. Although White was called out by the judge one day for making derogatory comments to a TV reporter about the prosecution case, White was respectful and soft spoken on the witness stand.
When Flanagan made a mistake and called him "Dr. Shafer" a few times, White said, "I'm honored."
The prosecution asked for more time to study the computer program White used before cross-examining him. Superior Court Judge Michael Pastor granted the request, saying he too was baffled by the complicated simulations of Jackson's fatal dose. He recessed court early and gave prosecutors the weekend to catch up before questioning White on Monday.
The surprise disclosure of White's new theory caused a disruption of the court schedule, and the judge had worried aloud that jurors, who expected the trial to be over this week, were being inconvenienced. But the seven men and five women appeared engaged in the testimony and offered no complaints when the judge apologized for the delay.
Prosecutors could call Shafer back during their rebuttal case to answer White's assertions.
Among the key issues is how White calculated that a large residue of propofol in Jackson's body could have come from the small dose that Murray says he administered. Shafer assumed Murray had lied, and he estimated Jackson actually was given 1,000 milligrams of the drug by Murray, who he said left the bottle running into an IV tube under the pull of gravity. White disputed that, saying an extra 25 milligrams self-administered by Jackson would be enough to reach the levels found in his blood and urine.
White also said a minuscule residue of the sedative lorazepam in Jackson's stomach convinced him the singer took some pills from a prescription bottle found in his room. He suggested the combination of lorazepam, another sedative, midazolam, plus the propofol could have killed Jackson.
"It potentially could have lethal consequences," said White. "... I think the combination effect would be very, very profound."
White's testimony was expected to end Murray's defense case after 16 witnesses. It likely will be vigorously challenged by prosecutors, who spent four weeks laying out their case that Murray is a greedy, inept and reckless doctor who was giving Jackson propofol as a sleep aid in the singer's bedroom. Experts including Shafer have said propofol is not intended to treat insomnia and should not be given in a home.
White's theory was based on urine and blood levels in Jackson's autopsy, evidence found in Jackson's bedroom and Murray's long interview with police detectives two days after Jackson died while in his care.
While accepting Murray's account of drugs he gave Jackson, the expert's calculations hinged on the invisible quotient: Jackson's possible movements while his doctor was out of the room. With no witnesses and contradictory physical evidence, that has become the key question hanging over the case.
Those who knew the entertainer in his final days offered a portrait of a man gripped by fear that he would not live up to big plans for his comeback concert and worried about his ability to perform if he didn't get sleep. He was plagued by insomnia, and other medical professionals told of his quest for the one drug he believed could help him. He called it his "milk," and it was propofol.
Jurors have now seen it up close as both Shafer and White demonstrated its potential use as an IV infusion.
With White's testimony, the defense sought to answer strong scientific evidence by the prosecution. But they did not address other questions such as allegations that Murray was negligent and acting below the standard of care for a physician.
Flanagan, the defense attorney, produced a certificate from Sunrise Hospital in Las Vegas showing Murray was certified to administer moderate anesthesia, referred to as "conscious sedation." However, the document showed several requirements including that the physician "monitor the patient carefully" and "provide adequate oxygenation and ventilation for a patient that stops breathing."
Medical witnesses noted that Murray left his patient alone under anesthesia and did not have adequate equipment to revive him when he found him not breathing.
The coroner attributed Jackson's June 25, 2009, death to "acute propofol intoxication" complicated by other sedatives.