HBO Max's "The Staircase" Is Based on an Unsettling Real Story

18 years after the release of Jean-Xavier de Lestrade's docuseries "The Staircase," the story of Kathleen Peterson's death is being turned into a scripted series on HBO Max. In March 2021, Variety reported that HBO Max was adapting the case for an eight-part limited drama, also titled "The Staircase." Emmy-winning actor Toni Collette is portraying Kathleen, and Oscar-winning actor Colin Firth is taking on the role of Michael Peterson, Kathleen's husband who was convicted of her murder in 2003.

The show's cast also includes Sophie Turner, Michael Stuhlbarg, Juliette Binoche, Dane DeHaan, Olivia DeJonge, Rosemarie DeWitt, Tim Guinee, Patrick Schwarzenegger, Vincent Vermignon, Odessa Young, and Parker Posey. Antonio Campos's "The Staircase" will explore the life of the Peterson family in North Carolina, the circumstances surrounding Kathleen's suspicious death, and Michael's involvement.

While it's unclear how much of the infamous case the HBO Max series will cover, its teaser trailer, which arrived on March 29, hints that it may shed light on the tragic events from the Peterson family's perspective. Campos and "American Crime Story" writer Maggie Cohn both serve as co-showrunners and executive producers for the series.

Before "The Staircase" premieres on May 5, here's what you need to know about the strange true story behind Kathleen's death.

On Dec. 9, 2001, Michael called 911 after supposedly discovering Kathleen lying in a pool of blood at the bottom of a staircase in their home. While on the phone, he told dispatchers that she was unconscious but still alive. However, by the time paramedics arrived, Kathleen was dead. He also told paramedics that Kathleen had been drinking that night, but experts found her blood alcohol content to be below the legal driving limit. According to CNN, scientists examined her body at the scene and found her injuries consistent with a death by homicide. These injuries included seven deep lacerations on her head, scrapes and bruises on her face, and a crushed thyroid. Blood drops were also found on Michael's clothing along with a bloody shoe print on Kathleen's sweatpants.

During the 2003 trial, prosecutors put forth the idea that Michael had murdered before and was looking to cash in on Kathleen's $1.4 million life insurance policy. CNN reported investigators also discovered gay pornography on Michael's computer, suggesting the idea that he and Kathleen had fought over his sexuality. The defense brought in their own forensic expert, who argued the scene's blood-spatter evidence was consistent with an accidental fall. The investigation and trial lasted two years, resulting in Michael's conviction and a sentence of life in prison without the possibility of parole.

In 2010, Duane Deaver, the state's blood-spatter expert for the case, was accused of forensic incompetence. A judge then found that Deaver's testimony had been misleading and a former North Carolina attorney general stated that any evidence gathered while Deaver was at the scene could be inadmissible in a new trial. After he spent eight years in prison and six years out on bond, CBS News reported that Michael accepted an Alford plea — which concedes that the prosecution has sufficient evidence to convict but the defendant does not admit guilt — to the lesser charge of manslaughter in 2017. He was sentenced to time served.

Prosecutors felt that Kathleen's death was eerily similar to the death of Elizabeth Ratliff, a coworker of Michael's first wife, Patty. Elizabeth is the biological mother to Michael's adopted daughters, Martha and Margaret. When Michael was being investigated for Kathleen's death, prosecutors took another look at the circumstances surrounding Elizabeth's 1985 death in Germany, exhuming her body in 2003. According to CNN, a forensic pathologist who worked on Kathleen's case, Deborah Radisch, came to the same conclusion that Elizabeth's death resembled that of Kathleen's and classified it as a homicide. While Elizabeth's autopsy was updated to indicate that she died from homicidal assault, and prosecutors for Kathleen's case used the evidence to draw parallels in court, Michael was never formally charged with her death.