Dr. Charles Czeisler -- a Harvard University sleep expert who reviewed observations and emails written by people surrounding Jackson during preparation for his "This Is It" tour -- testified Friday in a wrongful death suit that Jackson's request to use a teleprompter to perform some of his classic songs "was shocking and indicated to me the profound impact this sleep deprivation was having on his memory."
Czeisler said the sleep deprivation was due to overuse of the surgical anesthetic, propofol, which records indicate Jackson's doctor, Dr. Conrad Murray, had been administering to the singer for two months before he died at age 50 in June 2009.
Murray is serving a four-year prison sentence for involuntary manslaughter in Jackson's death.
Czeisler said Jackson's reported symptoms of weight loss, paranoia, anxiety, chills, difficulty with balance and an inability to perform his dance steps were consistent with sleep deprivation and the abuse of propofol.
He said based on records he reviewed, Murray ordered more than 4 gallons of propofol between April 2009 and June 2009, which Czeisler called a "a stupendous amount."
Czeisler's testimony is part of a lawsuit Jackson's mother, Katherine Jackson, and his three children, Prince Michael, Paris and Prince Michael II, brought against concert promoter AEG Live for wrongful death. They allege the company was at fault because it failed to hire an appropriate physician for the pop star, then neglected to supervise the singer properly.