Firth plays the role of American novelist Michael Peterson, who was accused of murdering his wife, Kathleen (Collette), in 2001. 

He claimed she died after falling down the stairs at their home, but police suspected he bludgeoned her to death and staged the scene to look like an accident. According to Variety, Posey will play Freda Black, an assistant district attorney and prosecutor. The previously announced cast of the series also includes Juliette Binoche and Rosemarie DeWitt. 

Antonio Campos of ''The Devil All the Time'' fame will direct six episodes of the series. He will also serve as writer and showrunner along with Maggie Cohn. 

HBO Max has ordered eight episodes of the limited series, which is based on the docu-series of the same name and various books and reports on the Peterson case.