Alberto Alvarez will testify Wednesday at a preliminary hearing against Dr. Conrad Murray about the doctor’s attempts to revive the singer on June 25, 2009, his attorney said.

The bodyguard’s testimony could provide key corroboration to the prosecutors’ argument that Murray’s actions demonstrated “an extreme deviation from the standard of care” by administering the powerful anesthetic propofol without the proper equipment, and also concealing it and botching efforts to resuscitate the singer.

An autopsy report found Jackson died from an overdose of propofol.

Deputy District Attorney David Walgren said Tuesday that Murray forced Alvarez, 34, to gather and conceal items before calling 911 to try to help Jackson. Walgren told a judge that he would present evidence that Murray waited much as 21 minutes before calling for paramedics.

At the end of the preliminary hearing, which was expected to go into next week, a judge will rule whether there is enough evidence for Murray to stand trial on an involuntary manslaughter charge in the pop star’s death. He faces up to four years in prison if convicted.

The Houston cardiologist has pleaded not guilty, and his attorneys have contended he did not give Jackson anything that “should have” killed the singer.

On Tuesday, Jackson friend and choreographer Kenny Ortega described how the singer appeared sick during one rehearsal days before his death and left early. The rehearsals were for a series of planned comeback concerts in London.

Ortega said after that incident, Murray “was upset that I had sent Michael home the night before and didn’t allow him to rehearse.”

The hearing, attended by international media and fans, provided another glimpse into the private life of Jackson, a one-time superstar who grew reclusive after his acquittal on child molestation charges in 2005.

He was described fondly by former workers, even though the singer wouldn’t allow staff into his bedroom or even the second floor of his rented mansion.

It was in that room that Walgren said Murray was providing Jackson propofol roughly six times a week since being hired as the singer’s personal physician in May 2009. It was also in that room where Jackson died, the prosecutor said, long before help was summoned.

Another bodyguard, Faheem Muhammad, testified that he saw Jackson lying on his bed, his eyes and mouth wide open, when he arrived. He described Murray as panicked, and that the doctor asked whether anyone knew CPR.

The hearing was expected to include testimony from police, coroner’s officials and forensic experts who will describe the mix of sedatives found in Jackson’s system.

Preliminary hearings have a lower burden of proof than trials, and defense attorneys rarely present a case. Murray’s attorney, Ed Chernoff, did not make an opening statement.

The 57-year-old cardiologist passed notes to his attorney, but did not speak during Tuesday’s proceedings.