LOS ANGELES (AP) ― While the defense was on the verge of its counter attack in the trial of Michael Jackson’s doctor, the prosecution dramatically shifted the focus from personalities to science ― its most powerful weapon in the courtroom battle.

Its star witness, a scientist with a reassuring witness box manner, had jurors on their feet straining for a better view of his show-and-tell demonstration. It was the closest they would come to seeing a purported re-enactment of how the King of Pop died.

Dr. Conrad Murray, charged with causing Jackson’s death, watched intently as Dr. Steven Shafer closed the case against him holding a bottle of propofol, an IV bag and a tube carrying the milky white liquid downward.

That was how it happened on June 25, 2009, said Shafer. He was certain.

On Monday, a defense attorney will try to shake his testimony and later a fellow scientist billed as “the father of propofol,” will offer another theory. Whether Dr. Paul White can absolve Murray of blame for the singer’s death remains to be seen. But the defense is just beginning.

“He will have to stand firm on the fact that reasonable minds can differ,” said Marcellus McRae, a former federal prosecutor and trial attorney who has been following the case closely. “He will have to change the landscape here and show some reasonable doubt. The question is will this be enough.”

Murray, a Houston based cardiologist, has pleaded not guilty to involuntary manslaughter.

McRae said calling Shafer as the final prosecution witness was a master stroke.

“Brick by evidentiary brick, Shafer has built a wall of scientific reasons for the jury to conclude that Dr. Murray was criminally negligent,” he said. “It allows the prosecution to tell the jury that their case is built on science rather than shifting theories.”

In addition to making the science understandable, Shafer offered some colloquial phrases that may resonate with jurors including the words “crazy” and “clueless.”

He called Murray’s unorthodox use of propofol as entering “a pharmacological never-never land” and said the doctor was “clueless” when it came to helping his dying patient. And he denounced a defense theory that Jackson could have awoken from sedation and given himself the drugs that killed him during a few minutes that he was left alone by Murray.

“People don’t just wake up from anesthesia hell-bent to pick up a syringe and pump it into the IV,” Shafer said, reminding the jury that the procedure was complicated. “It’s a crazy scenario.”

Shafer stood in the well of the courtroom with an IV pole, a bag of saline solution and a bottle of propofol, showing how the drug could have run quickly into Jackson’s veins while his doctor was out of the bedroom.

He drew a scene in which Murray, lacking the proper equipment to measure doses, left Jackson on an IV drip of the powerful anesthetic flowing quickly under the pull of gravity into the sleeping singer.