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Los Angeles (CNN) -- Michael Jackson probably died after he rapidly injected himself with a dose of the surgical anesthetic propofol on top of a large dose of sedatives he swallowed when Dr. Conrad Murray was away, the defense's propofol expert testified Friday.
The prosecution theory of how Jackson died requires "an incredible coincidence of circumstances" using a "befuddling" IV drip configuration and an "irrational" assumption about how Murray injected sedatives, Dr. Paul White testified.
White, the last defense witness in Murray's involuntary manslaughter trial, challenged the assumptions used by prosecution anesthesia expert Dr. Steven Shafer to conclude that Jackson's death was caused by an infusion of the surgical anesthetic propofol set up by Murray.
Deputy district attorney David Walgren will take the weekend to confer with Shafer before beginning his cross-examination of White on Monday morning.
Closing arguments could be heard as soon as Tuesday in the trial that started a month ago, depending on how long the prosecution takes with its questioning of White and if it chooses to recall Shafer in rebuttal.
The defense theory is that a desperate Jackson, fearing that his comeback concerts could be canceled unless he found elusive sleep, self-administered propofol that Murray was trying to wean him off of. It contends that Jackson also swallowed eight lorazepam tablets while Murray was not watching.
Shafer conceded last week that it was possible that Jackson, not Murray, could have been the one to open the IV drip to a fatal pace, but prosecutors contend that it would make no difference in Murray's guilt.
Murray is responsible for Jackson's death even if he did not give him the final and fatal dose, because he was criminally reckless in using the surgical anesthetic to help Jackson sleep without proper precautions, the prosecution contends.
White testified Friday that it is his opinion Jackson died after he injected himself with a 25-milligram dose of propofol between 11:30 a.m. and noon June 25, 2009.
Testimony and phone records indicated it was about noon that Murray realized Jackson was not breathing.
White theorized that Jackson could have "pushed" the drug into an catheter in his leg using a syringe over a 15- to 30-second period, much faster than a doctor would have done.
"I believe it could potentially have lethal consequences," White testified.
White also concluded that Jackson swallowed a large dose of lorazepam several hours earlier, which would have left "a very high concentration" of the sedative in his body. "So you've got drugs that have additive or even synergistic effects, and I think the combination effect would be very profound," White said.
Shafer, who testified over an 11-day span for the prosecution, concluded the "only scenario" that fits the scientific evidence -- mainly the drug levels found in Jackson's blood after his death -- is that Jackson was on an IV drip of propofol for three hours before his death.
White, however, testified Friday that with such a flow of propofol, Jackson would have been "sleepy but arousable but breathing spontaneously." It would not have killed him, he said.
The 100-milliliter propofol bottle prosecutors believe Murray used was empty when investigators found it, leading Shafer to conclude that the last drops entered Jackson's body just as his heart stopped beating.
White called it "an incredible coincidence of circumstances" that the bottle would empty exactly when Jackson died.
The defense expert also questioned the prosecution contention that Murray placed the propofol bottle into an empty saline bag with an opening cut into it to suspend it from the IV stand next to Jackson's bed.
It would have been more logical for Murray to use a plastic suspension tab built onto the bottle, a routine practice.
"It's befuddling to me, because anyone picking up the bottle would naturally gravitate for pulling up the little hanger," White said. "Why would you go to all the hassle?"
Hanging the bottle inside a bag also would not work because if Jackson "rolled over and moved his leg, it would easily come out of the bag," White said.
The suspension tab on the propofol bottle had not been activated, both sides agreed.
Investigators who recovered the bottle and an opened bag testified they found them together, but they did not photograph it.
White also questioned Shafer's computer model conclusion that Murray gave Jackson at least nine four-milligram injections of the sedative lorazepam at regular intervals from 1:30 to 5 a.m. the day he died.
Those "enormous" sedative doses alone would have put anyone to sleep and possibly killed them, White said.
He said it would be "irrational" for a doctor to sit at Jackson's bedside and repeatedly injected the sedatives to a patient in very deep sedation, as Shafer's theory implies.
Friday's court session, which lasted only three hours, was attended by Michael Jackson's father, Joe, sister Janet and brother Randy. Brother Jermaine Jackson's daughter, Autumn, and Randy's son, Randy Jackson Jr., also sat in court. Kathy Hilton, who was a childhood friend of Michael Jackson's, and her husband, Rick Hilton were also in court Friday.