49 witnesses, 300 items of evidence – one anxious wait for Dr Conrad Murray

The jury is out in the trial of Michael Jackson's physician. Guy Adams summarises the key facts of the case

It was a long and no doubt lonely weekend for Conrad Murray, the physician catapulted to global notoriety two-and-a-half years ago when his client Michael Jackson suffered a fatal cardiac arrest on the eve of what was supposed to be his final comeback tour.

On Friday, a jury at Los Angeles Superior Court retired to consider its verdict after a six-week trial in which Dr Murray was accused of acting as an "enabler" who accepted an inflated salary to recklessly fuel his famous patient's addiction to dangerous prescription drugs.

Having spent the weekend mulling over the testimony of 49 witnesses (along with 300 items of evidence) the seven men and five women who will decide Dr Murray's fate are scheduled to meet today at 8am local time (4pm GMT) to continue formal deliberations.

In the court of public opinion, not to mention among the legal pundits who have been helping broadcasters make sense of the trial, Dr Murray has already been found guilty as charged. The circumstantial evidence against him seems persuasive; compelling, even. His defence team has been amateurish; the prosecution steady.

But there is no such thing as an open-and-shut case, particularly in trials which revolve around celebrity, and the jury's failure to issue an immediate verdict therefore suggests one of two things: either they are making sure to dot i's and cross t's, before delivering a unanimous (probably guilty) verdict; or, for now, they are divided. Here, in any event, are the key factors they have to weigh:

The charge

Dr Murray stands accused of "involuntary manslaughter", one of the milder forms of homicide, which in California carries a maximum sentence of four years in prison. It refers to the unintentional killing of a victim who dies because of the gross, reckless or criminal negligence of the defendant. And it is up to a jury to decide what constitutes that level of negligence.

The prosecution case

David Walgren, the prosecuting attorney, has claimed that Dr Murray killed Jackson through "greed", accepting a $150,000 (£93,500)-a-month salary on the basis that he would then administer Jackson with dangerous, prescription drugs. Against medical advice, Dr Murray secured him a domestic supply of propofol – the anaesthetic that eventually killed him – in order to combat insomnia. Having set up a slow drip to administer the drug, he then failed to properly observe his patient:

Phone records show that Dr Murray was speaking to a girlfriend when Jackson stopped breathing. After realising he was in trouble, the physician took 20 minutes to call emergency services, and was seen by eye-witnesses botching even basic efforts to revive him. While Jackson was being rushed to hospital, Dr Murray also failed to inform paramedics about the drugs in the singer's system.

The defence case

It has been a gruelling six weeks for defence lawyer Ed Chernoff, who had originally intended to call witnesses who would testify that Jackson was a hopeless drug addict, forced, because of impending bankruptcy, into embarking on a tour he was in no physical condition to complete.

However the judge, Michael Pastor, ruled them inadmissible, saying the trial should focus only on the events leading up to 25 June, the morning that the singer died.

The defence case heard in court therefore largely hinges on evidence presented by Dr Paul White, an expert witness. Dr White believes that blood and urine tests carried out during Jackson's autopsy suggest he was killed not by a steady feed of propofol (which a drip would provide), but by a single, large dose. That has helped Mr Chernoff to argue that Jackson administered a fatal injection of the drug himself.

The key questions

No one disputes that Jackson was killed by an overdose of propofol, and Dr Murray's own team concedes that the defendant had on occasion given him the drug at his rented home in Holmby Hills. On those grounds alone, the prosecution argues that a jury must convict: propofol should not be used outside a hospital setting, and is designed to be administered under close observation, which Dr Murray failed to provide, according to phone records.

The jury may also decide that eyewitness accounts of Dr Murray's actions immediately after Jackson fell ill, which included taking 20 minutes to call an ambulance, as well as misleading paramedics about the drugs in his system, and administering CPR when the singer still had a pulse (instead of checking his airways) constituted a level of professional negligence sufficient to produce a guilty verdict.

If they are unswayed by those lines of argument, their outcome of the trial will instead come down to a simple question: which of two star expert witnesses who were called to give evidence about propofol they choose to believe.

One is Dr Steven Shafer, a leading anaesthesiologist who was called by the prosecution. He said propofol is too strong to ever be used to treat insomnia, and believes levels in Jackson's blood and urine suggest that he was killed by an amount consistent with an intravenous drip.

The other, Dr White, was called by the defence. He argued that the blood and urine samples suggest that a single, large dose killed Jackson. Dr White believes the singer administered that dose himself, via a syringe.

That seems at odds with the absence of Jackson's fingerprints from any of the medical equipment at his bedside, but Dr Murray's team hope his testimony will nonetheless cast sufficient doubt to secure an acquittal.