A prosecutor has opened a hearing that will determine whether Michael Jackson's doctor will stand trial in the superstar's death by saying Jackson was already dead by the time help was summoned.

Dr. Conrad Murray appeared in a Los Angeles court Tuesday to begin a multi-day hearing during which prosecutors will lay out some of their evidence to support an involuntary manslaughter charge.

Prosecutor David Walgren says he will rely on Murray's statements to police, as well as text messages, phone records and expert testimony to show the doctor should stand trial.

He says evidence will show Murray waited at least 21 minutes to call 911 and ordered a bodyguard to help him clean up evidence before summoning help.

Murray has pleaded not guilty and his attorneys have said he did not give the singer anything that should have killed him.

THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.

LOS ANGELES (AP) _ Prosecutors are set to unveil their case against the man hired to look after Michael Jackson's health during rehearsals for his comeback tour as a judge determines whether the doctor should stand trial in the superstar's death.

Jackson's family and fans are expected to attend the hearing, which begins Tuesday with testimony from police, a coroner and medical experts about their search to find what killed Jackson and whether Dr. Conrad Murray was responsible.

In spite of an autopsy report attributing his death to acute intoxication of a powerful anesthetic complicated by other sedatives, the circumstances of Jackson's death are mysterious.

Prosecutors have suggested that Murray's lawyers will blame Jackson, claiming he may have injected himself with the fatal dose of propofol.

But that issue is unlikely to arise until trial.

The guardians of Jackson's legacy will be watching as the hearing focuses on the star's drug use. Executors of his estate have spent the last year and a half since his death burnishing Jackson's musical reputation, intensifying memories of his star power with the release of a movie, "This Is It," and an album, "Michael," featuring music he left behind.

The court proceedings, which are likely to lead to a lengthy trial, could open doors they would rather keep closed.

For Murray, the court case is the continuation of a nightmare. His dream job as Jackson's $150,000-a-month personal physician died along with Jackson on June 25, 2009, and, to make it worse, he stands accused of involuntary manslaughter.

Prosecutors have scheduled 30 witnesses to testify at the preliminary hearing before Superior Court Judge Michael Pastor.

Murray, 57, was hired to help Jackson prepare and to accompany him on his European comeback tour, entitled "This is It." But Jackson died between rehearsals, and Murray is accused of gross negligence when he administered propofol, which Jackson demanded to get to sleep.

The Houston cardiologist, who also has a clinic in Las Vegas, could face not only a prison sentence of up to four years, but the revocation of his medical license if he is convicted. Murray has pleaded not guilty, and his lawyer has said that nothing he did should have harmed Jackson.

An autopsy report found Jackson died from an overdose of propofol. In a statement to police, Murray acknowledged giving Jackson the drug and other sedatives to help him sleep, then briefly leaving the star's bedside. Cellular phone records show Murray made at least three personal calls around the time Jackson was stricken.

His lawyers claim the amount he administered could not have killed the superstar. That remains one of the key mysteries to be unraveled.