Los Angeles, March 8 (IANS) "Fifty Shades of Grey" star Dakota Johnson has signed on to star in and executive produce the upcoming historical courtroom drama film "Unfit".The film is based on Adam Cohen's 2016 book "Imbeciles: The Supreme Court, American Eugenics, and the Sterilization of Carrie Buck", reports variety.com.Buck was the plaintiff in 1927 Supreme Court case Buck versus Bell, which she lost. She had been sterilised three years earlier at the age of 18 under a Virginia law that legalised sterilisation of "undesirable" citizens. Buck died in 1983 at the age of 76."Like many, I was not privy to this shocking and fascinating moment in American history," Johnson said. "I quickly became obsessed with the prospect of shedding light on the massive misstep in American justice. Carrie Buck's story is poignant and galvanising, and certain aspects are unnervingly congruent with the relationship between the government and women today. "It is an important story that alongside RatPac and Amazon, I am honoured and eager to tell," she added.Other details about the film are yet to be revealed.