David Fournier, a certified nurse anesthetist who first worked with Jackson in 1993, said the singer was scheduled to receive some "facial work" in 2003 when Fournier canceled the procedure.
Everything was ready to go, he said, when Jackson arrived acting "a little goofy, a little slow to respond."
"I've known him for 10 years ... he was acting inappropriate," Fournier testified.
Fournier said he asked Jackson "if anything was going on" and whether he had taken any medication, which the singer denied.
"I didn't believe him," Fournier said, noting it was the last time Jackson called him for work.
About three months previously, Fournier said the singer stopped breathing during a dermatological procedure. Fournier said he had to "control" the singer's ventilation twice, and had to "assist" it at another point. That was an "unusual reaction" for Jackson, he said.
Fournier said he spoke to Jackson on the phone three days before that procedure when the singer called to wish him a happy birthday. Jackson's speech was slurred during that conversation, he said.
The anesthetist said he asked Jackson about the call when prepping for the June 2 procedure. The singer told him he was just tired, he said. Fournier said he "quizzed him extensively" about whether he had taken any recreational drugs or medication, but Jackson denied doing so.
"He was more than tired," Fournier said. "He was slurring his words."
Fournier was called to the stand as a defense witness in the wrongful death suit Jackson's mother and three children filed against AEG Live, the company behind the singer's ill-fated "This Is It" tour.
Katherine Jackson and her grandchildren allege the entertainment giant hired and negligently controlled Dr. Conrad Murray, who gave the singer a fatal dose of the powerful anesthetic propofol on June 25, 2009, two weeks before the London tour was set to begin. AEG says Michael Jackson hired Murray.
Murray is currently serving jail time after being convicted of involuntary manslaughter in Jackson's death.
Fournier spent Thursday morning describing the multiple times he assisted in Jackson's medical procedures, noting he gave the singer propofol 14 times between 2000 and 2003.
Jackson one time referred to the drug as "the milk," Fournier said, referring to its street name: "the milk of amnesia."
Overall, Fournier said he administered anesthesia to Jackson for procedures including scalp work, dental treatment, Botox and collagen injections, and "extensive tattooing" on the singer's lips and eyes.
Unlike most people who receive "a half-dozen" Botox injections, Fournier said, Jackson would get "hundreds of injections around the eye and face."
"He often needed to be sedated," Fournier said.
Fournier said he and Jackson became friends, describing him as a "very warm, likable guy." The two would discuss Jackson's medical history before each procedure, he said, as well as post-op instructions. Fournier recalled two occasions when Jackson disobeyed those instructions.