Tom Mesereau, who defended the star against child molestation charges in 2005, says Alberto Alvarez's credibility will be "attacked viciously" by attorneys for Dr. Conrad Murray, who's charged with involuntary manslaughter in Jackson's death.
In a document obtained by The Associated Press, Alvarez, who was Jackson's logistics director, tells investigators that, in the final, frantic moments of Jackson's life, Murray stopped CPR and started bagging up vials of drugs. Alvarez, who's the one who called 911 that day, also says Murray asked him to put the vials, along with an IV, into duffle bags.
"This witness, if believed," says CBS News legal analyst Lisa Bloom, "has evidence that Dr. Murray, at the moment of crisis, turned away from his patient, Michael Jackson, and decided to hide evidence. This is explosive."
The document obtained by AP describes a grim scene in the bedroom at Jackson's rented mansion the morning of June 25. The singer's mouth and eyes were said to be open, but there was no sign of life.
Murray is accused of giving Jackson the powerful anesthetic propofol to help him sleep, but the drug ultimately killed him.
Murray's lawyer, Ed Chernoff, asserts the allegations by Alvarez were leaked to hurt his client. Chernoff says in his statement that Alvarez's "statement was given more than two months after Michael Jackson's death and is inconsistent with a statement he gave the police the day after Mr. Jackson was taken to the hospital."
It is that inconsistency that Mesereau says Murray's legal team will focus on.
If the allegations are true, Mesereau told "Early Show" co-anchor Harry Smith Tuesday, they're "very damaging statements for the defense. Hiding evidence in a situation like this reflects a guilty conscience.
"However, do I think the defense is gonna attack this witness because, apparently, in prior interviews, he never mentioned this, and that's a very important issue. They're gonna attack his credibility. They're gonna investigate his background, as to whether he tells the truth in his life, and expect a real attack on this witness."
Which account is a jury more likely to believe?
"I think the defense is gonna say the more likely story is the one that was given closest to the time of the death of Michael Jackson. So, this witness is gonna be attacked viciously by the defense for making inconsistent statements in this investigation."
Murray is due back in court next month, when prosecutors are expected to officially lay out the evidence against him.
Jackson, 50, hired Murray to be his personal physician as he prepared for a series of comeback performances in London. He was participating in strenuous rehearsals and Murray would routinely meet him at the star's home in the evening for treatments.
The Los Angeles coroner ruled Jackson's death a homicide caused by an overdose of propofol and two other sedatives given to get the chronic insomniac to sleep.
Propofol is supposed to be administered only by anesthesia professionals in medical settings. Patients require constant monitoring because the drug depresses breathing and heart rate while lowering blood pressure, a potentially deadly combination.
Murray, 57, a cardiologist licensed in Nevada, California and Texas, has acknowledged briefly leaving Jackson's bedside the day he died, but maintained from the outset that nothing he gave the singer should have killed him. It wasn't illegal for him to administer propofol, though whether he followed proper procedures while Jackson was under the influence is a key part of the case.