LOS ANGELES (AP) — Michael Jackson was physically exhausted from a day of grueling rehearsals for his marathon 50-night comeback tour. But his nightly battle with insomnia had just begun. After showering and getting into bed, he called for his “milk,” a powerful drug he had been using to escape into unconsciousness.

Jackson saw the anesthetic known as propofol as his salvation. On June 25, 2009, it became the King of Pop’s death potion.

How he overdosed in his mansion on a drug intended for hospital use is at the centre of the manslaughter trial this week of the doctor he hired to be his highly paid personal physician for the “This is It” tour.

Testimony about the drug is expected to dominate the trial of Dr. Conrad Murray (pictured), a Houston cardiologist who has pleaded not guilty to a charge of involuntary manslaughter in Los Angeles Superior Court.

The prosecution claims Murray was grossly negligent in giving Jackson propofol at home without proper lifesaving equipment available and then left the room long enough to find his patient not breathing when he returned.

His defense team claims the singer, desperate for sleep, swallowed an additional dose of the drug when his doctor was out of the room.