Production on "Manson Girls" will begin this spring, Lo announced Monday at the Sundance Film Festival. Lo wrote the screenplay for the film which will examine the lives of eight young women who were followers of Manson.
The cast includes Taryn Manning, Heather Matarazzo, Tania Raymonde and Monica Keena.
Manson and three women followers were convicted in Los Angeles in 1971 of murder and conspiracy in the 1969 slayings of seven people, including actress Sharon Tate.
Lo said she became interested in the story when she realized she was living across the street from the house once occupied by Leno LaBianca and his wife, Rosemary, who were killed the next night.
She decided the most interesting element of the story was what made the girls fall under Manson's spell.
"I wanted to tell their early story when they were teenagers to before the Tate-LaBianca murders. That was much more fascinating to me. Why and how. How could this tiny, strange man from prison and almost a derelict completely attract all of these fantastic girls?" Lo said.
"I thought that was a very innovative way to tell the story," said Raymonde, who will play Manson follower Leslie Van Houten. "I thought that it wasn't exploitative at all ... and it wasn't putting any focus on Manson because I think one of the most interesting aspects is you never see him in the film."
Keena was so intent on playing Lynette "Squeaky" Fromme that she studied her intensely before her audition and now knows "everything about her."
"It gives you a chance to have some sort of empathy toward them that you might not have had before," Keena said. "I'm not saying you should forgive them, but there's a method to their madness, let's say."
Songs from the 1960s will help drive the story. Guy Allison of the Doobie Brothers will compose the music for the film.
Manson is serving a life sentence in a California prison. He has a devoted fan base, which concerns Manning.
"I'm a little worried about random weird fan mail but you can't really think about that," she said.