Attorney Ed Chernoff cross-examined Dr. Steven Shafer, who previously testified that the only plausible explanation for the death was that Jackson had been hooked up to an IV drip of the anesthetic propofol then left alone by Dr. Conrad Murray.
"That's a bold claim, isn't it," Chernoff asked.
"It's an honest statement," Shafer replied.
Chernoff also questioned the Columbia University researcher and professor about his IV demonstration for jurors on Thursday.
The defense attorney suggested Shafer had drawn conclusions that weren't necessarily supported by the evidence. Chernoff said the type of IV line that Shafer used in the demonstration was never found at Jackson's house.
Murray has pleaded not guilty to involuntary manslaughter. He could face up to four years behind bars and the loss of his medical license if convicted.
Shafer was expected to be the last witness called by the prosecution. After Shafer's testimony ends, defense attorneys will begin presenting their case.
In a development outside the presence of jurors, Superior Court Judge Michael Pastor set a Nov. 16 hearing to determine whether he should find defense expert Dr. Paul White in contempt for talking to a reporter on Thursday in violation of a gag order.
E! Entertainment reported Thursday on its website that White called either Shafer or Deputy District Attorney David Walgren a "scumbag."
White said in court that he didn't recall making the statement.
He told Pastor that he had talked to Walgren after the prosecutor pulled a tab from the side of a bottle of propofol that was recovered at Jackson's mansion.
He said he told Walgren it was "inappropriate to tamper with evidence found at the scene."
White and Shafer are colleagues at Columbia University and have known each other for nearly 30 years.
In a closed chambers meeting before court started on Friday, Walgren asked that White be expelled from the courtroom for the remainder of Shafer's testimony.
The judge declined, and Chernoff said he was embarrassed by the incident and he would ensure it didn't happen again. He said White had been hurt by Shafer's criticism of him during testimony.
Pastor previously ordered Chernoff's partner, Matt Alford, to appear at a contempt hearing over comments made during a network TV interview.