Michael Jackson's doctor tried to hide the fact that he had given the singer a powerful anaesthetic shortly before he died, a prosecutor has said. At a preliminary hearing, the prosecutor said Dr Conrad Murray phoned paramedics only after Jackson had died. Prosecutors say Dr Murray's negligence in treating the singer for insomnia led to his death aged 50 in June 2009. Dr Murray has pleaded not guilty to involuntary manslaughter, arguing he did not cause the singer's death. At the preliminary hearing, the judge is to decide whether prosecutors have enough evidence to try Dr Murray, a cardiologist. It is expected to last several days. Dr Murray faces up to four years in prison if convicted. 'Extreme deviation' In the courtroom in Los Angeles on Tuesday, prosecutor David Walgren said that when Dr Murray realised the singer had died, he ordered a security guard to collect medical paraphernalia and other items before having him call the authorities. Mr Walgren said Dr Murray had given Jackson a dose of propofol, a powerful surgical anaesthetic typically administered in a clinical setting, on the morning of 25 June 2009, after giving him various sedatives during the previous night. He said that Dr Murray did not properly perform CPR, and said that when paramedics did arrive, Dr Murray did not mention that he had given Jackson the drug. "The court will learn that in the opinion of these medical experts, there were a number of actions displayed by Dr Murray that showed an extreme deviation from standard medical care," Mr Walgren said, the Los Angeles Times reported. Mr Walgren said he expected Dr Murray's lawyers to claim that the pop legend had injected himself with the overdose. Also on Tuesday, Jackson's former personal assistant Michael Williams testified that as the singer's body lay in bed, Jackson's manager Frank Dileo told his children: "Daddy had a heart attack and died." Mr Williams testified that Dr Murray then said: "Don't say that, we don't know." Mr Williams also said Dr Murray had asked him to clear "cream" from the singer's bedroom "that he wouldn't want the world to know about". Mr Williams said he did not heed the request. Choreographer Kenny Ortega told the court that the singer had appeared unwell and out of shape in the days leading up to his death, and said he went home early from rehearsals. Jackson had been rehearsing for a series of highly anticipated concerts in London. The Los Angeles County coroner's office ruled the singer had died from an overdose of the surgical anaesthetic propofol, found in his body along with a cocktail of other sedatives. Source: BBC