With the investigation of Michael Jackson's death zeroing in on what drugs the pop singer took and who provided them, an upcoming toxicology report is key to whether anyone is criminally charged.

It's already known propofol, a powerful anesthetic not meant for home use, was among the drugs found in Jackson's rented mansion. The Los Angeles Police Department, working with the Drug Enforcement Administration and California attorney general's office, is trying to determine how the medications got there.

The coroner's toxicology report and the full autopsy results are not expected until the week after next. It will provide two important facts: whether propofol and any other drugs were present in the 50-year-old singer when he died June 25, and whether the levels were toxic.

"The quantity is key here," said Lawrence Kobilinsky, head of forensic science at John Jay College in New York. "Not only the presence, but the amount that has to be interpreted to see if it contributed to the death."

Kobilinsky sees propofol as "a smoking gun."

"There is no reason it should have been available to him. If it is a contributing factor to his death, then I think there would be criminal charges," he said.

The district attorney's office is in contact with police — a common practice during an investigation — but no evidence has been presented for possible charges, prosecutors' spokeswoman Sandi Gibbons said.

Police have said very little publicly. Chief William Bratton has said detectives are scrutinizing Jackson's prescription history and the doctors with whom he dealt, and haven't ruled out anything.

"Are we dealing with homicide? Are we dealing with an accidental overdose? What are we dealing with?" Bratton said last week.

Investigators obtained a search warrant and removed several bottles of propofol from Jackson's home, according to a person with knowledge of the investigation. The person is not authorized to speak publicly and requested anonymity.

Federal drug agents have contacted a major maker of propofol, Teva Pharmaceuticals, and drug distributor AmerisourceBergen Corp. Authorities asked AmerisourceBergen for sales data on propofol and its brand-name counterpart Diprivan to doctors, pharmacies and hospitals, company spokesman Michael Kilpatric told The Associated Press.

It's part of an effort to determine how the drug made it from the factory to Jackson's home. It's a mound of information, but investigators sorting through it have a critical edge: They're focusing on just a handful of doctors who hovered in Jackson's orbit, among them his longtime dermatologist, Dr. Arnold Klein, and recently hired personal physician Conrad Murray.

Police interviewed Murray two days after Jackson's death. Authorities say he is a not a suspect, though the cardiologist is a key figure in the investigation because he was with Jackson in the mansion and tried to revive him.

Edward Chernoff, Murray's lawyer, told the AP the doctor never gave or prescribed Jackson the painkillers Demerol or OxyContin, and said the doctor didn't give the pop star any drugs that contributed to his death.

Jackson had numerous medical procedures and took pain medication for years. Cherilyn Lee, a nurse who worked for Jackson but was not with him when he died, has said Jackson asked her for Diprivan, the brand-name version of propofol, to alleviate his insomnia. She refused.

Propofol and Diprivan are the drugs most widely used in the U.S. to induce general anesthesia. They can depresses breathing and lower the heart rate and blood pressure, so they are supposed to be administered by an anesthesia professional in a medical setting.

The propofol found in Jackson's home raises big questions.

"I can't think of a situation where it would be appropriate in the home setting," said Dr. David Zvara, anesthesia chairman at the University of North Carolina at Chapel Hill.

The American Society of Anesthesiologists issued guidance on the drug in 2004. Any doctor using propofol should have the education and training to manage anesthesia complications and "be physically present throughout the sedation," it says. Patients "should be monitored without interruption" for signs of trouble, and rescue equipment "must be immediately available."

An ordinary doctor without special training is "absolutely not" qualified to do give the drug, Zvara said.

Klein's relationship with Jackson also is being probed. Assistant Chief Coroner Ed Winter, following up on a subpoena, went to Klein's office this week seeking medical records on Jackson. Klein's attorney, Richard Charnley, has said his client is cooperating.

In TV interviews, Klein said he sedated Jackson for past medical procedures but never gave the pop star an unnecessary dose of drugs.

To retrace Jackson's drug history, investigators have provided the California attorney general's office with the names of several doctors and several aliases Jackson is believed to have used to score prescriptions. Those names, which have not been disclosed, were run through the state's prescription monitoring database, which has more than 100 million detailed entries of prescriptions written in California for regulated narcotics, such as Demerol.

"We found some things," Attorney General Jerry Brown said.

He wouldn't give specifics, but said the information would include how many prescriptions a doctor wrote, when the prescriptions were written, how much of a drug was prescribed and the strength of the drug. Because propofol is not monitored by the DEA, it would not show up in the state's database.

The work is painstaking.

"Stars use phony names and there's more than one doctor, there's doctor shopping," Brown said. "There's a lot of people in on the act."

(AP July 17, 2009)