Two experts took the witness stand Thursday in defense of Michael Jackson's doctor Conrad Murray, who is being tried for involuntary manslaughter of pop icon Michael Jackson.

Dr. Robert Waldman, an addiction expert, testified the escalating doses of Demerol as showing that the singer had become immune to its potency and seemed to have a dependency on the drug.

Waldman gave that conclusion relying on Klein's records from March 2009 until the days before Jackson died.

Klein was Jackson's longtime friend and dermatologist.

Some handwritten notes of Klein showed that he was giving Jackson huge doses of powerful Demerol from March through June, 2009, with 775 milligrams of Demerol along with small doses of the sedative Versed over three days in April.

This is a large dose for an opioid for a dermatology procedure in an office, Waldman said.

Waldman's testimony showed both Klein and Murray were giving Jackson some powerful drugs at the same time, while Murray didn't know Jackson was being treated by Klein and was receiving other drugs.

The defense called Waldman to testify in an effort to show Jackson's insomnia could have been caused by withdrawal from Demerol shots the day he died.

Dr. Paul White, who has been researching the use and effects of propofol since 1983, said that after reviewing the reports in the case, he cast doubt that Murray was responsible for Jackson's death.

I was somewhat perplexed at how a determination has been made that Dr. Murray was infusing propofol, White said. It wasn't obvious to me, I thought there were questions.

White is expected to resume his testimony on Friday and he is expected to counter the conclusions of prosecution anesthesiologist Dr. Steven Shafer, who made a demonstration of IV drip system in Dr. Conrad Murray's involuntary manslaughter trial.