[cnn-photo-caption image=http://i2.cdn.turner.com/cnn/2009/SHOWBIZ/Music/08/12/jackson.pharmacy.doctor/art.conrad.murray.undated.jpg caption="Dr. Conrad Murray, Jackson's personal physician, has had his home and office searched."]
Michael Jackson had "some very unusual problems" that Dr. Conrad Murray did not know about when he was hired to be Jackson's personal physician as the singer prepared for his comeback concerts, Murray's lawyer says.
Attorney Ed Chernoff - in comments published in the Los Angeles Times and confirmed Thursday by his spokeswoman - said his client did not know what drugs Jackson might have been taking or if he was addicted.
"When he accepted the job, he was not aware of any specific requirements regarding medications that Michael Jackson was taking or any addictions that he was suffering from," Chernoff told the Times.
Chernoff, in a quote confirmed by his spokesman, said that it was only after Murray moved to Los Angeles in May 2009 that "he realized that Michael Jackson had some very unusual problems."
Murray did not conduct drugs tests on Jackson and had no way of knowing, other than from Jackson's words, if he was taking other drugs, Chernoff's spokeswoman, Miranda Sevcik, told CNN.
Investigators, trying to determine if anyone should be charged in Jackson's death, have searched Murray's home and two clinics for evidence of drugs he may have given the singer.
One search warrant implied that police suspect Jackson was a drug addict. It said there was "probable cause to believe" the searches would uncover evidence of excessive prescribing, prescribing to an addict, prescribing to or treating an addict and manslaughter.
It also cited "probable cause to believe" that the premises contained "records, shipping orders, distribution lists, use records relating to the purchase, transfer ordering, delivery and storage of propofol (Diprivan)."
Chernoff told the newspaper that he believed investigators expected to find evidence that Murray prescribed drugs other than the anesthetic propofol to Jackson.
"I have no doubt they came up completely empty in that regard," he said.
A source with knowledge of the investigation told CNN that Murray gave propofol - commonly known by the brand name Diprivan - to Jackson in the 24 hours before he died.
Chernoff has refused to confirm or deny if Murray administered propofol to Jackson, although he denied "unequivocally" that Murray gave Jackson painkillers.
The Los Angeles County coroner's office said Monday that it has completed a "thorough and comprehensive" report into what killed Jackson, but police have requested that the report not yet be released because of the ongoing investigation.
A former prosecutor who has also defended doctors in medical malpractice cases involving anesthesia said prosecutors would face "a very, very severe uphill battle" when charging a doctor with manslaughter.
"You have to prove gross recklessness in the prescription of drugs," Paul Callan told CNN Wednesday. "That's really hard with a doctor because doctors are always prescribing drugs; patients occasionally die from them, that's not criminal conduct. But here, you have to show that this doctor should've known Jackson was an addict and that he could've died from these drugs."
In addition to the local probe, federal drug investigators have focused on Murray, according to a law enforcement official. DEA agents have accompanied Los Angeles detectives during the searches of Murray's Houston, Texas, clinic and his home and clinic in Las Vegas, Nevada.
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