An authority on the drug propofol testified at the trial of Michael Jackson's doctor on Wednesday that he wants to dispel fears about the anesthetic that led to the pop star's 2009 death.

Dr. Steven Shafer, regarded as one of the leading researchers in the use of propofol, said that propofol, which is normally used to sedate patients before surgery and not as a sleep aid as Jackson used it, had gotten a bad name since it was ruled the main cause of Jackson's death.

But he testified it was an outstanding drug when administered in the right setting.

Shafer is expected to be the last prosecution witness as the involuntary manslaughter trial of Dr. Conrad Murray resumed in Los Angeles after a five-day break.

Murray, has admitted giving Jackson propofol as a sleep aid. But his attorneys have claimed Jackson gave himself an extra, fatal dose of the drug when Murray was out of the singer's bedroom.

Medical examiners determined Jackson's June 25, 2009, death resulted from an overdose of propofol combined with sedatives.

Shafer told jurors; I am asked every day I'm in the operating room, I tell patients what I'm going to do and I am asked the question, 'Are you going to give me the drug that killed Michael Jackson?'

Shafer, who teaches at Columbia University, said he is testifying without pay, in part because he wants to restore patients' faith in propofol when it is used in the correct circumstances.

What has happened in this case has nothing to do with (patients') experience when they see a doctor for a procedure, Shafer said.

Previous prosecution witnesses have harshly criticized Murray for giving Jackson propofol at the singer's home and without sufficient monitoring and safety equipment.

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