A key point of contention has emerged in the case investigators are piecing together about the death of Michael Jackson: Exactly when did Dr. Conrad Murray realize that his patient had stopped breathing?

There are currently two accounts of that moment on June 25, and about an hour separates them.

According to police documents, Murray told detectives he put Jackson to sleep with drugs just minutes before he found the singer not breathing around 11 a.m., then let nearly 90 minutes go by - much of that time on his cell phone - before an ambulance was called.

But Murray's lawyer says the doctor didn't discover a stricken Jackson until around noon.

Investigators have ruled Jackson's death a homicide, based on tests showing he was killed by the combination of the anesthetic propofol with at least two sedatives, a law enforcement official told The Associated Press, speaking on condition of anonymity because the finding has not been publicly released.

The homicide designation does not necessarily mean a crime was committed, though it's a helpful starting point should prosecutors choose to seek criminal charges. Police have said Murray is the target of an investigation into manslaughter, defined as a homicide without malice or premeditation.

Murray told police he spent the morning of June 25 administering various sedatives to Jackson in an attempt to get him to sleep, according to an affidavit for a search warrant served last month on Murray's clinic in Houston. Unsuccessful in inducing rest, the doctor ultimately gave in to the singer's demands for a dose of propofol around 10:40 a.m.

By 11 a.m., after a short trip to the bathroom, Murray said he saw Jackson was not breathing and began trying to revive him, both with a "rescue" drug and by performing CPR, according to the documents. An ambulance was not called until 12:21 p.m. and Murray spent much of the intervening time making non-emergency cell phone calls, police say.

That timeline is flawed, said Murray's attorney, Edward Chernoff, who was present when investigators spent three hours interviewing the doctor June 27. Chernoff said Murray never told police he found Jackson not breathing at 11 a.m. - instead, it was more like noon.

"Their theory is he came back and wasn't breathing. That's not what Dr. Murray told them," Chernoff said Tuesday. "They are confusing the time Michael Jackson went to sleep with the time he stopped breathing."

Chernoff did not provide additional detail about what Murray had told police.

Home use of propofol is virtually unheard of - safe administration requires lifesaving equipment and a trained anesthesiologist monitoring the patient at all times. While the 25 mg dose Murray said he gave Jackson was relatively small, its combination with the sedatives lorazepam and midazolam proved deadly.

Even if Murray found Jackson around noon, he still waited too long to call an ambulance, said one medical expert, adding that anyone - including doctors - should make calling an ambulance their first priority.

"In a situation like that, time is life," said Dr. Douglas Zipes, an Indiana University heart specialist and past president of the American College of Cardiology. "It's got to be immediate or you are going to lose the individual."

Phone records show Murray spent 47 minutes between 11:18 and 12:05 making three personal calls. One of the calls was to one of Murray's offices, Chernoff said, adding that the doctor never told investigators about the calls because he wasn't asked about them.

At 12:13 p.m., Murray made a four-second call to Jackson's personal assistant, Michael Amir Williams, pleading for help, Williams' attorney Carl Douglas said. Within two minutes, Williams called Alberto Alvarez, Jackson's bodyguard, with a similar plea.

Douglas, who also represents Alvarez, said the bodyguard hurried to the top floor of Jackson's rented mansion, a private sanctum where staff were not normally allowed, and assisted a confused-looking Murray as he frantically tried to revive Jackson. It was Alvarez that placed the 911 call at 12:21 p.m.

Douglas said Alvarez might be able to shed some light on Murray's actions but, two months after the death, police investigators had still not formally interviewed his client and had only spoken fleetingly with him at the hospital immediately after Jackson was pronounced dead.

Douglas said he was "dismayed at the seeming haphazard manner investigators have gone about obtaining information."

Deputy Police Chief Charlie Beck declined to comment, citing the continuing investigation.

Chernoff did not provide additional detail about what Murray had told police. Early on in the case, the lawyer released a statement saying his client didn't give any drugs that "should have" killed Jackson. Asked to elaborate on the statement, Chernoff said: "I stand by that assertion and I believe that will be borne out in time."

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