Michael Jackson had more of the sedative lorazepam in his blood stream than his doctor admitted giving him on the day he died, a top anesthesiology expert testified on Thursday.

Dr. Steven Shafer, the last prosecution witness in the involuntary manslaughter trial of Dr. Conrad Murray, also said that propofol is not fatal when swallowed, undercutting a former, controversial defense theory.

Authorities ruled that Jackson's June 2009 death was caused by an overdose of the anesthetic propofol, combined with effects of lorazepam.

Murray has admitted giving Jackson a dose of propofol and four milligrams of lorazepam to help him sleep. But his attorneys have argued that Jackson gave himself extra doses of both drugs without Murray's knowledge.

Shafer said on Thursday that based on the timing of when Murray said he gave Jackson the lorazepam, those doses would have amounted to only 10 percent of the amount of the drug found in Jackson's blood stream at autopsy.

It's only 10 percent of what was measured, so this did not happen, Shafer said.

Prosecutor David Walgren said, The blood levels proved that there is more than four milligrams of lorazepam administered to Michael Jackson?

Absolutely, said Shafer.

Shafer also said that both animal and human studies have shown that propofol is barely absorbed into the bloodstream when swallowed because most of it is eliminated by the liver.

Murray's lawyers announced in court last week that they were dropping the theory that Jackson swallowed propofol by himself. However, they continue to maintain that he injected himself with more of the anesthetic, which is normally used to sedate patients before surgery.

Shafer on Wednesday sharply criticized Murray's care of the 50-year-old pop star, and gave 17 instances egregious violations of common medical standards.

He said that giving propofol at home to treat insomnia was a pharmacological 'Never Never Land' that had only been done to Jackson.

The defense is expected to cross examine Shafer later on Thursday and begin presenting its case on Friday. Murray, who has pleaded not guilty, faces a maximum sentence of four years in prison if convicted.