Al Pacino and Susan Sarandon are starring in the HBO film You Don't Know Jack, which airs Saturday, and paints a very different portrait of Jack Kevorkian, the man who helped terminally ill patients die, and who was once vilified in newspapers as Dr. Death. Check out the trailer and a behind-the-scenes featurette for TV Movie below.

Pacino plays the former pathologist who helped 130 patients end their lives over a 10-year period before being sent to prison in 1999 for second-degree murder.

"Jack Kevorkian is a person you think you know. But at the end of the story, you find yourself saying 'He's different than I would have thought he would be,' " Pacino said recently.

But the Oscar-winning actor didn't meet Kevorkian, now 81 and out of prison, before filming began.

"There are characters you do meet with, and it works, and there are some you don't. I don't know why," Pacino told journalists, saying he had simply "absorbed" Kevorkian in preparation for the role.

Kevorkian invented two devices -- the Thanatron (death machine) and Mercitron (mercy machine) -- to pump lethal drugs or gas to terminally ill individuals, and performed his first assisted suicide in 1990.

After numerous trials, he was eventually convicted in 1999 of second-degree murder after allowing a videotape of one such suicide to be aired on national television.

He was sentenced to 10-25 years in prison, released on parole in 2007 due to good behavior, and now gives occasional public lectures.

Since 1990, three U.S. states have voted to allow assisted suicide under certain guidelines, but the practice is still a criminal offense in most of the U.S.

Susan Sarandon, Brenda Vaccaro and Danny Huston play Kevorkian's real-life Hemlock Society activist friend, his sister and his defense attorney, respectively.

"I don't think it's about sympathizing or empathizing with Jack. I think it's about understanding him -- the choices he made, who he was," said writer Adam Mazer.

"I think we show a very honest portrayal of the man -- his foibles, his strengths, weaknesses and flaws," Mazer said.