The Peterson case has already built a large cult following in the true crime world, teeing up The Staircase to be a smash on the streaming service. In addition to the docuseries, production also has Michael Peterson’s two books to draw from: Behind the Staircase, and Beyond the Staircase. They will need as much background information as possible if they plan on depicting flashbacks with Kathleen. And based on the fact that they’ve enlisted powerhouse Collette to play her, Kathleen is likely going to have a leading role.
Originally from https://screenrant.com/staircase-series-toni-collette-cast-hbo-max/