The doctor charged in the death of pop star Michael Jackson collected evidence from the scene before having an ambulance called when he found the singer unconscious, a prosecutor said on Tuesday.

The accusations came during a preliminary hearing in the trial of Dr. Conrad Murray, who was caring for Jackson when he died of a drug overdose on June 25, 2009, and is charged with involuntary manslaughter in the singer's death.

Los Angeles Deputy District Attorney David Walgren said more than 20 minutes passed between the time Murray discovered the 50-year-old pop star in his bed not breathing and when a member of Jackson's security team called paramedics.

"It is important that at this point 911 (emergency service) has not been called or ordered to be called by Dr. Murray," Walgren told the judge in the packed Los Angeles courtroom, which included reporters and members of Jackson's family.

"Instead, Dr. Murray is having (a security guard) assist him in collecting medical evidence and various paraphernalia," he said.

Jackson died after a dose of the powerful anesthetic propofol that is typically used in surgery but which Jackson asked for as a sleep aid.

Murray, a Houston-based doctor with a second practice in Las Vegas, was hired to care for Jackson in advance of a series of concerts in London that were to have begun in July.

Walgren said that that after the pop star returned from a rehearsal in the early morning hours of June 25, 2009, Murray gave him doses of several drugs to calm him down, starting with Valium at 1:30 a.m. and ending with an injection of propofol between 10:40 a.m. and 11 a.m.

KENNY ORTEGA TESTIFIES

Walgren said that Murray was on the phone at 11:51 a.m., and at around noon noticed Jackson had stopped breathing.

A Jackson security guard called 911 at 12:21 p.m. to summon paramedics, Walgren said. Afterward, Murray went to UCLA Medical Center with Jackson, but Walgren said that Murray was less than forthcoming with doctors.

"Most notably Dr. Murray would not tell these UCLA doctors about the propofol treatment, let alone the nightly propofol treatment he had been giving Michael for the past two months," Walgren said.

Walgren said propofol is not used in home settings, and he said he would call expert medical witnesses to testify that Murray had "deviated from the standard of care."

Attorneys for Murray did not make opening statements to the court on Tuesday, but they did cross-examine witnesses.

In the preliminary hearing, prosecutors will offer evidence to advance their theory, and a judge will determine if the facts are strong enough to bring Murray for a full trial, possibly in front of a jury.

Murray has admitted giving Jackson propofol, but has pleaded not guilty to the charge.

In a separate hearing last week, Walgren said prosecutors believe the defense will claim Jackson may have died by injecting himself with propofol.

Following Walgren's opening statement, Jackson collaborator Kenny Ortega testified that he encouraged Jackson to leave a rehearsal early on June 19, 2009 because the singer seemed withdrawn and not well, and that with Ortega's encouragement the pop star went home early. Ortega testified that he was called to a meeting the next day, where Murray scolded him.

"Dr. Murray told me that this was not my responsibility and asked me not to act like a doctor or psychiatrist, but to be the director of the show, and to leave Michael's health to him," Ortega said.