The legal admission came as a senior cardiologist slammed doctor Conrad Murray over his handling of Jackson's care on June 25, 2009, when the King of Pop died aged 50 from an overdose of propofol.
"We are no longer contending that propofol was orally ingested in this case," said Michael Flanagan, a member of Murray's legal team fighting to clear the medic of a charge of involuntary manslaughter.
Murray is accused of giving Jackson an overdose of propofol while trying to help him sleep. His lawyers claim Jackson was a desperate addict who gave himself a fatal extra dose while Murray was out of the room.
The 58-year-old doctor has admitted to giving Jackson 25mg of propofol around 10:40 am on the day he died, after the star had been awake all night, despite being given a series of doses of other less powerful sedatives.
The theory that Jackson could have drunk some more propofol, which the star referred to as "milk," while Murray was out of the room has been countered by evidence that no propofol was found in his stomach.
The lawyers have also claimed that Jackson could have injected an extra dose of propofol, via an intravenous (IV) tube in his leg, while Murray was out of the room for two minutes to go to the bathroom.
Meanwhile cardiologist Alon Steinberg, a senior member of the California Medical Board, accused Murray of a series of mistakes over his treatment of Jackson, including crucially leaving to go to the bathroom.
"When you monitor a patient, you never leave their side," he told the court. "It's like leaving a baby that's sleeping on your kitchen countertop," he added.
The trial in Los Angeles Superior Court is expected to last five weeks, until the end of October. If Murray is convicted, he faces up to four years in jail.