In November 2000, Cascio said, a house doctor at a New York City hotel was all too willing to provide Jackson with meds.
"The house doctor gave him what he wanted," Cascio said. "And, again, the house doctor was in awe and so intrigued just to be around this man."
Cascio confronted Jackson, but to no avail.
"I said, 'You don't want to end up like Elvis, do you?' And [he said] 'I would never end up like Elvis. I don't have a problem,'" Cascio said. "He was upset that I would even bring this up and talk to him about this."
Jackson's sister, Rebbie Jackson, and brother, Tito Jackson, said earlier this week that they too tried to get through to Jackson. Tito Jackson said his brother's security team got in the way.
"I got into physical fights with his security team," he said. "The public didn't know, but we did many times try and they kept him away like he was the president of the United States."
Cascio described Michael Jackson as a "situational addict."
In the weeks leading up to his death, that addiction seemed to include propofol, also known as Diprivan, a powerful anesthetic injected intravenously, often used to sedate patients before surgery.
Chopra remembered Jackson asking him about the drug.
"On one occasion ... he said to me, 'Deepak, did you know there's something that takes you right to the edge, to the valley of death, and it brings you back? Do you know anything about it?'" Chopra said.
On May 12, 2009, Murray put in a staggering bulk order for propofol -- more than 40 gallons worth. Jackson died some seven weeks later after receiving a fatal dose of the drug.
"It was a pharmaceutical experiment on Michael Jackson," prosecutor David Walgren said during his closing argument on Thursday. "It was an obscene experiment in 2009 done by a doctor with no sleep medicine training. It was criminal gross negligence."
Many music legends have died from accidental drug overdoses, but only Michael Jackson had a doctor by his side.
Cascio, who believes Murray should be in jail, said Jackson once confided in him that he feared he would die from a gunshot. But, Cascio said, no one would have ever thought that a shot of a prescription drug would claim Jackson's life so prematurely.
ABC News' Christina Ng contributed to this report.