A sleepless Michael Jackson spent his last hours pleading for a dose of a powerful anesthetic, his doctor told police, according to court records unsealed Monday.

For six hours, Dr. Conrad Murray said he resisted -- fearful that the pop star had developed a dangerous addiction to propofol.

Instead, Murray administered the sedatives Valium, lorazepam and midazolam -- five times over six hours. But none put Jackson to sleep, and he continued to demand his "milk," the word the pop star used for propofol.

Murray finally relented and at 10:40 a.m. added the drug to Jackson's intravenous drip, according to the records.

That dose -- mixed with the cocktail of other sedatives in the pop star's system -- was enough to kill him, the Los Angeles County coroner's office concluded in a preliminary toxicology report cited in a search warrant affidavit unsealed Monday in Houston.

These documents address one of the central questions in the Jackson death investigation: What killed him. The coroner's office, according to the records, said it found "lethal levels" of propofol in Jackson's system.

The records also lay out the first detailed chronology of Jackson's final hours-- and reveal Murray's fateful decision to give Jackson the drugs despite his suspicions that the pop star was becoming addicted to them. The narrative is based largely on a three-hour interview Murray gave to Los Angeles police detective two days after Jackson's death on June 25.

Authorities still have not disclosed how Jackson or Murray obtained the propofol, which is typically used in hospitals by anesthesiologists. Another unanswered question is exactly when Jackson stopped breathing. Both are crucial to the criminal investigation.

Police said Murray told them he found Jackson not breathing at 11 a.m. -- a contention that Murray's attorney disputes -- but paramedics were not called until nearly 90 minutes later. During that time, police suspect that Murray made three cellphone calls totaling 47 minutes, according to the affidavits filed last month when authorities sought search warrants for Murray's Houston medical office and storage unit.

In addition, Murray failed to tell paramedics or emergency room doctors that he had administered propofol, a critical omission that calls into question his treatment and could bolster pursuit of an involuntary manslaughter charge, authorities said.

"Michael Jackson was not the usual patient with the usual problems in the usual circumstances," said Murray's attorney, Edward Chernoff, in response to the court records. "Dr. Murray's overriding goal was to try to help him. . . . To place negligence on him simply because he was there, I don't think is fair."

Authorities have sought records from at least five different physicians who treated Jackson as well as pharmacies in Las Vegas and Beverly Hills, but Murray is the only one named in court documents as the target of the manslaughter investigation. Jackson had specifically asked concert promoter AEG Live to hire Murray as his $150,000-a-month personal physician to travel with him to London, where he was scheduled for a 50-concert comeback tour.

At Jackson's request, Murray had been administering 50 milligrams of propofol in the six weeks prior to his death using an intravenous line, according to court records. But after weeks of use, Murray said he tried to wean the pop star off the medication. Murray told detectives that he lowered Jackson's dosage to 25 milligrams and mixed it with two other sedatives, lorazepam and midazolam. Then, on June 23, two days before Jackson's death, he administered those two medications and withheld the propofol -- and Jackson was able to sleep.

On June 25, the day Jackson died, Murray once again tried to induce sleep without resorting to propofol, according to the affidavit. He first gave Jackson the three alternative sedatives at 1:30 a.m., 2 a.m., 3 a.m., 5 a.m. and 7:30 a.m. But Jackson remained awake.

Finally, "after repeated demands/requests from Jackson," Murray relented and gave Jackson 25 milligrams of propofol, diluted with another sedative, records state.

Medical experts said that a 25-milligram dose for someone Jackson's size should not have been enough to kill him. But combined with other drugs, the propofol could have been more dangerous.

"You start giving a lot of drugs and don't know what the final effects might be," said Dr. Scott Engwall, vice chairman of the Department of Anesthesiology at UC Irvine School of Medicine. "When you give a little bit of this and a little bit of that, it starts adding up."

According to the court records, Murray sat at Jackson's bedside for 10 minutes after the singer fell asleep, before leaving to use the restroom for no more than two minutes. When he returned, he found Jackson not breathing and said he immediately began administering CPR as well as a drug to reverse the effects of the sedative. Police said that Murray told them that Jackson had stopped breathing about 11 a.m. Murray's attorney disputed that contention.

Police believe Murray made three separate phone calls for approximately 47 minutes beginning at 11:18 a.m, according to records and law enforcement sources. Jackson's staff did not call 911 until 12:21 p.m., police said.

Murray's attorney criticized the timeline outlined in the document as "theory, not fact" and disputed the significance of the phone calls.

"Dr. Murray never said 10 minutes. He said he watched him long enough that he felt comfortable," Chernoff said. "Their theory is he . . . goes off to make some social calls and comes back and finds Michael Jackson is dead and is negligent. The implication is that he left the room to make the phone calls. He didn't need to leave the room to make the calls."

Chernoff declined to say why Murray did not immediately tell paramedics and emergency room doctors that he had given Jackson propofol.

Deputy Chief Charlie Beck of the Los Angeles Police Department would not comment directly on the warrant other than to call it "true and accurate." He said the investigation is ongoing and that the findings would be forwarded to county prosecutors who will ultimately determine whether to file any criminal charges.