The Sky Atlantic show sees her playing Kathleen Peterson, the wife of American novelist Michael Peterson (played by Colin Firth) who was convicted of killing her and sentenced to life in prison in 2003, despite maintaining she had died after falling down the stairs.
In 2017, Peterson was released after his charge was reduced to manslaughter and he was sentenced to time already served.
In the series, Collette acts out a number of the scenarios that could have led to Kathleen’s death, all of which lead to her gruesome end on the stairs.
In a recent interview with Variety, Collette said she had just one chance to nail each of the three death scenes, which were carefully choreographed to match the conditions that Kathleen was really found in.
“I had to really clear my mind and get out of the way for each take,” she said.
“I remember sitting at the bottom of the stairs before a take, shutting everything out and talking to Kathleen in my head. I did not expect this to happen but it did. I know it sounds weird. I think it was about permission and getting it right for her.”
As for what she thinks really happened to Kathleen, Collette said: “I really don’t know. It’s like life itself: The more you know, the more you realise you don’t know.”
Collette was nominated for an Emmy for her performance as Kathleen, as was Firth for his turn as Michael.
The real Michael Peterson raged against the dramatisation in a June interview, saying documentary-maker Jean-Xavier de Lestrade had “pimped” him and his family out.
“He released his archive to [The Staircase showrunner Antonio Campos] who then created a fictional account of events,” Peterson said. “Most of which trashed me, which I really don’t care about, and my children, which I really do care about.”
The Staircase is available to stream on Now.