Anaesthesia expert Dr Paul White came to the defence of Jackson's physician, arguing that the singer could have administered the powerful agent after an initial dose by Murray wore off.
White added that Jackson may have swallowed up to eight additional lorazepam pills without Murray's knowledge on the day of his death in June 2009, creating a lethal cocktail of drugs.
White said that his self-injection theory matched with Murray's statement to police and was supported by a lack of IV bags and leads in Jackson's bedroom displaying propofol residue.
He also said that an extra 25 milligrams self-administered by Jackson would be enough to reach the levels found in the star's urine and blood.
The prosecution had previously suggested that Jackson died after Murray administered him an IV drip infused with propofol.
White also claimed that the amount of lorazepam found during an autopsy on Jackson's body was much greater than the two doses Murray admitted to administering.
"The fact that there is even a tiny amount of free lorazepam [in the stomach] is consistent with the theory that he took lorazepam orally," White told the court.
The court recently heard from Murray's defence that Jackson had been warned of the dangers of his medication and that it was likely he was addicted to painkillers.
The trial is due to resume on Monday (October 31) after the prosecution requested more time to analyse the methods White used when coming up with his theory.