TIMELINE: Michael Jackson's Final Days

June 23, 2010— -- It was to be Michael Jackson's first concert series in a dozen years, billed as one of the greatest comebacks of all time. When Jackson himself arrived in London to announce his tour, no one dreamed that in less than four months, the King of Pop would be dead.

Jackson's sudden, unexpected death raised suspicions and questions that still linger today, a year after his death.

As the entertainer's personal physician awaits trial on manslaughter charges for allegedly administering the overdose of intravenous and prescription medications that killed him, those who knew Jackson and spent time with him in the months before his death disagree about his state of mind.

Watch the full 2-hour special, "Michael Jackson: After Life," Friday on "20/20" at 9 p.m. ET.

Some say Jackson was happier than he'd been in years. Meanwhile, others paint a picture of a man whose health was unraveling, worsened by a severe addiction to prescription drugs, including the intravenous anesthetic propoful, reportedly to combat chronic insomnia.

Propofol is normally only used in hospital settings with a trained anesthesiologist who monitors the patient's heart rate and breathing continually while they are unconscious during surgery. Propofol can trigger cardio-respiratory effects that are potentially fatal.

"This is way off the chart,'' said Vesna Maras, a former Los Angeles deputy district attorney. "This, this is not even FDA-approved for insomnia. It is not a sleep aid. You look at what is this stuff? It's an anesthetic agent that is used to put somebody under, basically knock them unconscious. So in other words, it would be like using a hammer to kill an ant."

What follows is some of what is known about the final days and hours of Jackson's life.

The documentary "This is It," just released on DVD, provides a roadmap of Jackson's last days as he prepared for his tour.

At first glance he seemed confident and in control.

"I gotta cue that ... that shouldn't trigger on its own,'' said Jackson, still lithe and youthful at 50, in footage of a concert rehearsal.

A famous perfectionist, Jackson "was not going to settle,'' said Travis Payne, the show's choreographer. "He wouldn't allow any of us to settle."

"I think he was happier than he had been in years."

Jackson's former manager, Frank DiLeo, told ABC News: "I saw a guy that wanted to perform. But he wanted to do it right. And he was strong enough. He was working out every day. If he wasn't healthy, if there was something wrong, I would have stopped him. No. There was nothing to stop."

But DiLeo and other concert executives were concerned that Jackson was losing weight and not sleeping. "He said he wasn't sleeping," said DiLeo. "And I said to him, 'Well, what seems to be the problem?' 'Well, I'm just excited. You know, I'm all wound up.'"

"We were concerned," said Randy Phillips, the show's promoter. "I hired someone whose job it was to be sure that he eats... [Director Kenny Ortega] would cut Jackson's chicken breast for him, and say, 'Eat! Eat!'"

On Easter 2009, registered nurse Cherilyn Lee said Jackson had called her, frantically begging for propofol, the intravenous anesthetic, saying he needed it to sleep.

"He said, 'Find me an anesthesiologist. I don't care how much money they want,'" Lee recounted.

Lee said she warned Jackson. "Michael...I love you as family," she said she told him. "I would not give this to anyone. This is not a safe medicine. Please don't take this."

"And I said, 'The problem with you telling me you want to be "knocked out"' -- those are his word,-- 'is that you might not wake up the next morning.' I mean the last end result of this is death. I said, 'You don't want to do this.' He said, 'No, my doctor said it's safe. It works quick and it's safe. As long as somebody is here to monitor me and wake me up, I'm going to be OK.'"

On June 21, Lee received a foreboding call from a Jackson aide. Lee said Jackson's aide told her the singer needed to see her right away.

"I could hear Michael in the background: 'Tell her. Tell her that one side of my body is hot, is hot, and one side of my body is cold, it's very cold,'" Lee said. "And I said, 'tell him he needs to go to the hospital.'

"I knew that somebody had given him something that hit that central nervous system," she said. "He was in trouble."

The concert executives were concerned that Jackson was losing weight and not sleeping. "We were concerned," said Randy Phillips, the show's promoter. "I hired someone whose job it was to be sure that he eats... [Director Kenny Ortega] would cut Jackson's chicken breast for him, and say, 'Eat! Eat!'"