Witness David Fournier told jurors he had worked with Jackson for a decade until the relationship ended in 2003, when Fournier refused to participate in a medical procedure.
Jackson was acting "goofy" and was slow to respond to standard questions before a scheduled cosmetic surgery that was canceled after Fournier refused to administer an anesthetic, he said.
The incident came a few months after Fournier said he had to help Jackson breath while undergoing another procedure and later determined that Jackson had not disclosed a new medical condition.
"He wasn't honest with me," Fournier said without detailing the change in Jackson.
At the time, Jackson had an implant in his abdomen to block the effects of Demerol and other opiate drugs.
Fournier testified that he had given the singer a relatively large dose of a powerful anesthetic and needed to know how Jackson was going to react.
A judge ruled that Fournier couldn't testify about the implant because he learned about it from Jackson's dermatologist, and it was a hearsay statement.
Jurors, however, had heard about the device through videotaped testimony of another Jackson doctor on Wednesday.
Fournier testified as a defense witness in a negligence case filed by Jackson's mother against AEG Live LLC, the promoter of Jackson's comeback shows.
Katherine Jackson claims the concert promoter failed to properly investigate the doctor who was later convicted of involuntary manslaughter for giving Jackson an overdose of the anesthetic propofol as a sleep aid in 2009.
AEG denies it is liable for Jackson's death. Its lawyers have said Jackson hid his prescription drug use from nearly everyone.
Fournier said his incomplete medical records show he administered propofol to Jackson at least 14 times between 2000 and 2003. He estimated he gave the singer the drug numerous other times over the years for a variety of cosmetic and dental procedures.
He noted in his records that Jackson had a high tolerance for certain drugs, which Fournier said could be attributed to a variety of factors, including genetics.
During cross-examination, Fournier said Jackson never requested any specific drugs, including propofol, during procedures or asked to be sedated for longer than was necessary. He said the singer didn't exhibit any drug-seeking behavior or signs that he was doctor-shopping.
Fournier said he knew that Jackson had received an above-average number of anesthetic treatments over his lifetime, and many were related to procedures needed after Jackson was badly burned in a shoot for a Pepsi commercial in 1984.
Fournier said it was not common to administer an anesthetic during cosmetic procedures, but the ones done on Jackson were complex and involved dozens of injections. Some of the procedures were near Jackson's eye and sedation was necessary to keep him still, Fournier said.
Fournier also said he never had any indication that the singer was using propofol as a treatment for insomnia.
Jackson's physician Conrad Murray had been giving the singer nightly doses of propofol as Jackson prepared for his ill-fated "This Is It" shows.
Anthony McCartney can be reached at http://twitter.com/mccartneyAP