LOS ANGELES (AP) — Dr Conrad Murray's use of a cocktail of drugs on Michael Jackson as he struggled to fall asleep on the day he died was a "recipe for disaster" and ultimately caused his death, a UCLA sleep therapy expert testified Thursday.

Dr Nader Kamangar described Murray's treatment as "unethical, disturbing and beyond comprehension."

Under questioning by Murray's attorney, J Michael Flanagan, the witness was asked to tell jurors what he knew about the events of June 25, 2009, the day of Jackson's death.

"To summarise, Mr. Jackson was receiving very inappropriate therapy in a home setting, receiving very potent therapies without monitoring," Kamangar said.

He said diazepam (Valium), lorazepam (Ativan) and midazolam (Versed) were given to the sleepless star during a 10-hour period throughout the night and morning.

"This cocktail was a recipe for disaster," Kamangar said.

Noting the addition of propofol (Dipravan), a powerful anaesthetic used in surgeries, Flanagan asked: "Could this have caused death?"

"Absolutely," Kamangar said. "Absolutely".

Authorities say Murray gave Jackson a fatal dose of propofol. Murray has pleaded not guilty to involuntary manslaughter.

The witness, one of the experts who evaluated Murray's actions for the California Medical Board, expressed dismay about the drugs Murray gave the pop star, his failure to immediately call for help, and his lack of monitoring and record-keeping.

Murray was unable to produce any written records on his treatment of Jackson, Kamangar noted.

"It is an egregious violation of the standard of care when you are using sedatives like propofol and you are not writing it down," Kamangar answered.

Kamangar was the third prosecution expert to criticise the conduct of Murray. He said his first mistake was using propofol to treat insomnia, calling it an unacceptable application of the drug.

He said Jackson's demand for the drug — the subject of previous testimony — was not a sufficient reason to give it. He also suggested Murray should have done a physical examination, taken a history from his patient about his insomnia, and called in other medical experts if necessary to evaluate the problem.

"The most important thing he should have done is call for help," Kamangar said.

He said Murray's interview with police made it clear that he waited too long to call for an ambulance when he found Jackson not breathing.

On Wednesday, Murray's defence team announced they were dropping a claim that was the centrepiece of their case -- that Jackson swallowed additional propofol when Murray was out of the room. Flanagan did not bring up self-dosing on Thursday.

Before court recessed, the prosecution called to the stand Dr Steven Shafer, one of the nation's leading experts on propofol. However, he did not get into his substantive testimony before trial recessed until Monday because Shafer had a schedule conflict.

Shafer was expected to be the final prosecution witness in the case. The defence has a colleague of Shafer's waiting to take the stand.

Shafer helped craft guidelines for appropriate propofol dosing for sedation that is included in the packaging of every bottle that is sold.

Murray could face up to four years behind bars and the loss of his medical licence if convicted.