Actor Al Pacino said he decided not to meet record producer and convicted killer Phil Spector before portraying him in an movie - only to find he already had.

A friend showed Pacino a 20-year-old photo in which the actor was standing next to Spector, but Pacino said he had no memory of the moment.

The HBO film, Phil Spector, which debuts in March, focuses on the client-lawyer relationship between Spector and Linda Kenney Baden, who represented him in his first trial after he was charged with the murder of actress Lana Clarkson.

That ended in a mistrial, but Spector was convicted in a second trial and is now serving 19 years to life in prison.

Pacino wore a dizzying array of wigs in his portrayal of the eccentric Spector, whose Wall of Sound style was an integral part of pop music in the early 1960s.

The actor said he decided not to meet Spector in prison because he would be a different man than the one Pacino is portraying, who had not yet been convicted of a crime.

He watched video clips of Spector to help him with his portrayal.

"I didn't know anything about him, except that he was responsible for a lot of great music and this strange case," Pacino said.

Helen Mirren, who portrayed Baden, said she heard stories about Spector from her film-maker husband Taylor Hackford, who had hired Spector to provide music for his 1980 film The Idolmaker.

Dame Helen was a last-minute substitute in her role. Bette Midler had begun filming as Baden, but had to withdraw because of a bad back. The film's executive producers are Barry Levinson and David Mamet.