Colin Firth as Michael Peterson
The novelist was accused of murdering his
second wife, Kathleen Peterson, in December 2001. Prior to her death, the couple had been together for more than 10 years, creating a blended family with 5 children between them.
After years of court battles and prison time, Michael—who maintains his innocence to this day—entered an Alford plea to manslaughter in 2017. In an Alford plea, the accused submits a guilty plea in court and acknowledges that the prosecution likely could present evidence that would convict him, but continues to assert his innocence.
Michael released a memoir called Behind the Staircase in 2019. As of 2022, he was 78.
Toni Collette as Kathleen Peterson
The former Nortel executive died in December 2001. Michael found her covered in blood at the bottom of their Chapel Hill home's stairs, sparking a controversial homicide investigation. The case is now considered closed after Michael entered an Alford plea.
Kathleen was 48 at the time of her death. She had one daughter named Caitlin.
Michael Stuhlbarg as David Rudolf
Hired as Michael's defense attorney in 2001, brash David Rudolf became a central figure in The Staircase's initial episodes, as well as the Netflix sequel released in 2018. He continues to work as a criminal defense lawyer and recently published the book American Injustice about his most famous cases.
Olivia DeJonge as Caitlin Atwater
Although Kathleen's daughter, Caitlin, initially supported her step-father, Michael Peterson, in the days immediately following her mother's death, she later became convinced of his guilt. In 2017, she told Indy Week she remains steadfast in her belief, saying that after the first trial, "I felt confident that I knew what happened. I knew what happened to my mom. While there's no true closure that can ever come for an event like this, for a loss this deep, I was ready to walk away and start moving forward with my life."
Dane DeHaan as Clayton Peterson
Clayton is Michael Peterson's eldest son from his first marriage. One of his dad's biggest supporters, Clayton has long believed that his step-mom Kathleen died in a terrible fall. The 2018 Staircase sequel showed Clayton raising two children with longtime partner Becky. He is now 46.
Patrick Schwarzenegger as Todd Peterson
Todd is Michael's younger son from his first marriage. Like his brother, Clayton, Todd is adamant that his father is innocent. He has since made a career for himself in business and real estate, which he often promotes on his Instagram.
Clayton and Todd's mother and Michael's first wife, Patricia Peterson, died of a massive heart attack in July 2021.
Odessa Young as Martha Ratliff
Following both of her parents'deaths, Michael Peterson and his wife at the time, Patricia, were granted custody of Caitlin and Martha in 1985 and have called him "dad" ever since. She said in the 2018 documentary that she supports her adopted father.
Sophie Turner as Margaret Ratliff
Margaret took an active role in supporting her father's case, even supporting the exhumation of her birth mother's remains to aid in his defense. She remains a steadfast supporter to this day.
According to IMDb, Margaret has worked in the film and TV industry.
Parker Posey as Freda Black
Black was a lead prosecutor in the first Peterson trial, where she delivered the closing arguments. In 2018, she was found dead from end-stage liver disease due to chronic alcoholism at the age of 57.
Tim Guinee as Bill Peterson
In the documentary, Michael's lawyer brother, Bill, stepped in to offer his brother emotional support and to help with the formation of his legal team.