"The search warrant authorized law enforcement to search for and seize items, including documents, they believed constituted evidence of the offense of manslaughter," Chernoff said in a statement posted on his firm's Web site.
Authorities did not disclose what information was taken and say they still do not consider Murray a suspect.
In the four weeks since Jackson's death, rumors have proliferated about what killed him. Several members of Jackson's family have said they suspect foul play. Investigators appear to be focusing on a powerful anesthetic, propofol. The drug was found in the Beverly Hills mansion Jackson was renting, according to a person with knowledge of the investigation who is not authorized to speak publicly.
While doctors regularly moved in and out of Jackson's life - including those who prescribed him pain medication over the years - it was Murray who joined Jackson's entourage in May as the King of Pop prepared for a series of comeback concerts in London. On June 25, Murray found Jackson unconscious in a bedroom of the mansion, Chernoff has said, tried to revive him and ultimately helped summon paramedics.
While Jackson went into cardiac arrest, it's still not known what caused his death at age 50. An autopsy was conducted but results are not expected until next week. The Jackson family had a second autopsy performed, and those results also are pending.
Police have twice interviewed Murray, including at the Los Angeles hospital where Jackson was taken and pronounced dead. The coroner's office wanted its own interview, which the lawyer agreed to; it may happen Friday without Murray present, according to Miranda Sevcik, Chernoff's spokeswoman. Chernoff would answer questions on the doctor's behalf.
"Based on Dr. Murray's minute-by-minute and item-by-item description of Michael Jackson's last days, he should not be a target of criminal charges," Chernoff had said in a statement a day before the raid. "Dr. Murray was the last doctor standing when Michael Jackson died and it seems all the fury is directed toward him."
Murray is currently in Las Vegas. There was no sign of activity Wednesday at Murray's medical offices in Las Vegas. Doors were locked and curtains drawn at his practice, Global Cardiovascular Associates.
Los Angeles Police spokesman Gus Villanueva insisted Wednesday that Murray still is not considered a suspect, saying, "There is no crime report to list him as a suspect."
All the more reason that it was a surprise Murray's attorney would allude to a manslaughter investigation - giving more details than what authorities have been willing to say.
Manslaughter requires proof there was a reckless action that created a risk of death or great bodily injury. If a doctor is aware of the risk, there might also be an issue of whether the patient was made aware of that risk and decided to take it.
Showing gross negligence or recklessness would be the challenge facing prosecutors, who on Wednesday said they are waiting to see whether investigators bring them a criminal case.
"We have not been presented with any evidence. We have not been asked to evaluate anything," said district attorney's spokeswoman Sandi Gibbons.
The search of Murray's office hard drive indicates authorities are looking not just for patient records but also for e-mails either between the doctor and Jackson or orders for prescription drugs, said Harland Braun, a prominent Los Angeles defense attorney who has represented doctors in cases involving administration of drugs.
The Drug Enforcement Administration already has contacted a major maker of the anesthetic propofol, as well as a national distributor of the prescription drug. Propofol's emergence in the Jackson case has surprised many medical experts, who point out that the drug can depress breathing and lower the heart rate and blood pressure and must be administered properly by a trained expert who is monitoring the patient. Typically, that's in a hospital operating room.
Jackson's former nutritionist told The Associated Press that she worked with Jackson between January and April, when he began persistently asking for the powerful anesthetic.
On Wednesday, Los Angeles County coroner's officials who are piecing together Jackson's medical history subpoenaed records related to nutritionist Cherilyn Lee's treatment of Jackson, according to Lee's spokeswoman, Belinda Foster. The registered nurse is cooperating with investigators but required a subpoena because the records were protected by law, Foster said.
The coroner's office did not return calls seeking comment.
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