The court proceedings of the involuntary manslaughter trial of Michael Jackson's personal physician scheduled for Monday have been put off for two days, a court spokeswoman said.

The postponement was due to the "unavailability of a prosecution witness," Mary Hearn from the Los Angeles Superior Court told Xinhua.

Steven Shafer, one of the key prosecution witnesses, had been scheduled to continue his testimony but will not be available because of a death in his family, said Hearn.

Shafer, an anesthesiology expert who began testifying last Thursday, is expected to give a detailed explanation of how propofol, a potent surgical anesthetic drug, works, including how it is metabolized.

Jackson died on June 25, 2009 at his rented Holmby Hills estate when he was preparing for his comeback series of 50 sold-out London concerts. The Los Angeles County Coroner's Office ruled the King of pop died of "acute propofol intoxication."

Shafer's testimony is expected to take at least a day and was scheduled to be followed by the defense team's presentation.

Prosecutors seek to prove the 58-year-old physician, Conrad Murray, has failed to properly monitor Jackson after giving him a lethal dose of propofol. They contended that the cardiologist " repeatedly acted with gross negligence, repeatedly denied appropriate care to his patient, Michael Jackson, and that it was Dr. Murray's repeated incompetence and unskilled acts that led to Mr. Jackson's death on June 25, 2009."

Defense attorneys argued that Murray was weaning Jackson off the medication. The cardiologist was hired by Jackson to care for him two months before his death.

Murray, who was set free on a bail of 75,000 U.S. dollars, faces up to four years in prison and the loss of his medical license if convicted of the felony charge.