Former Doctor Who star Smith, who was first rumoured to take on the role in January, will be joined by Suki Waterhouse as Mary Brunner, an early Manson follower.
Charlie Says will centre on the three young women – Susan Atkins, Leslie Van Houten and Patricia Krenwinkel – who were sentenced to death after the 1969 Tate-LaBianca murders. The killings were carried out on Manson’s orders and the victims included actress and model Sharon Tate, the pregnant wife of director Roman Polanski. After California abolished the death penalty, the trio’s sentences were commuted to life imprisonment. The film will follow Atkins, Van Houten and Krenwinkel as they face up to the reality of their crimes.
Game of Thrones actress Hannah Murray, Odessa Young and Marianne Rendon will play the three women and Carla Gugino, Kaylie Carter and Merritt Wever are also set to star.
American Psycho director Mary Harron will helm the film which is written by Guinever Turner.
Production on Charlie Says begins in LA this spring.