National Medal of Arts recipient, actor Al Pacino acknowledges the applause after receiving the medal from US President Barack Obama at a ceremony in the East Room of the White House in Washington, February 13, 2012. [Photo/Agencies]

Playwright David Mamet had little interest in legendary music producer and convicted murderer Phil Spector, dismissing him as a "freak" - until he watched a documentary that shed light on a complicated personality.

Related: HBO to make adaption of AIDS play

Now, the "Glengarry Glen Ross" writer is bringing to HBO a movie inspired by Spector's life that imagines his relationship with the attorney who defended him against charges of killing actress Lana Clarkson in Los Angeles in 2003.

The film, "Phil Spector," written and directed by Mamet, stars Al Pacino as the music producer and Helen Mirren as his attorney.

Related: Serpico: Pacino played me better than I did

When Mamet's agent urged him to watch a documentary about Spector, the playwright said he felt he already knew enough about the eccentric producer who sported wild hair and was found guilty of murder.

"You start out saying this guy's a freak," Mamet told reporters at a Television Critics Association meeting on Friday.

Learning more about Spector, "you start to think, how could I be so prejudiced? The guy sounds brilliant."

"Then you say, maybe he's not guilty," Mamet said.

In the TV film that debuts March 24 on Time Warner Inc-owned HBO, Mirren plays Linda Kenney Baden, who defended Spector in his first murder trial that ended in a mistrial with jurors deadlocked. He was convicted in a second trial in 2009 and is serving a sentence of 19 years to life.

Spector, now 73, revolutionized pop music in the 1960s with his layered "Wall of Sound" production techniques, working with the Beatles, the Ronettes, Cher and Leonard Cohen at the height of his fame. But for years before the trial, he had lived as a virtual recluse in a mock castle in suburban Los Angeles.