Scrolling through Michael Stuhlbarg’s filmography on Wikipedia, you’ll notice that quite a few of his roles are written in blue font, with hyperlinks that lead to other Wikipedia pages. The real-life characters he’s taken on include former New York Times executive editor Abe Rosenthal in “The Post,” Golden Age-actor Edward G. Robinson in “Trumbo,” and even disgraced pharmaceutical executive Richard Sackler on “Dopesick.”

But Stuhlbarg says his role as defense attorney David Rudolf on “The Staircase,” HBO Max’s adaptation of the true crime docuseries, was his hardest biographical challenge yet.

“I’ve played a lot of people who’ve actually lived, some of whom are still alive and some who are not,” Stuhlbarg told Variety. “I had played a criminal defense lawyer briefly on a ‘Law and Order’ episode once before, but never with the amount of depth or time or as much information to sift through as I had under these circumstances.”

The real Rudolf, now 72, had a daunting task ahead of him when he agreed to represent Michael Peterson (who’s played by Colin Firth) after he was accused of murdering his wife, Kathleen (Toni Collette) at the bottom of their home’s back staircase. As captured in the original docuseries, Peterson is a frustrating client — appearing to lie even when telling the truth, and not especially forthcoming about the troubling details of his past. From failing to disclose the details of a close friend’s death to fudging a story during a failed mayoral campaign about receiving a Purple Heart in Vietnam, Peterson did not make Rudolf’s job easy. (Peterson was sentenced to life in prison in 2003 before being released on house arrest in 2011. He was fully freed in 2017 after entering an Alford plea.)

Rudolf became known by viewers of the docuseries as a stalwart fixture of the North Carolina courtroom, remaining by Peterson’s side even as the case took unpredictable and shocking turns, with Rudolf committed to maintaining his composure in public, yet struggling behind the scenes. Playing a lawyer fiercely devoted to his job, Stuhlbarg said he was interested in learning why Rudolf “thrives doing what he does.”

“It was really challenging,” Stuhlbarg said of taking on the role. “Some days, it was eerie, because I had his voice ringing in my head. Other days it felt very much like me going through those circumstances. And that’s just part of the journey that we go on.”

Variety spoke with Stuhlbarg about his experience meeting the real Rudolf, his own theories about the case and why he believes his character said yes to a French documentary crew capturing the case in real time.

When you first came to the project, what was your familiarity with “The Staircase”?

I had seen the documentary, and I had actually started watching it a second time before I even knew that I was going to be involved in this project. There was something about the story that kept my attention all the way through. So the idea of exploring it from David Rudolf’s shoes was a thrilling idea for me, because I found him to be one of my favorite — if you could say this — characters in the documentary to watch because of his thought process, because of his sense of humor, because of the way he navigated his way through through the circumstances that he was given. Then I got to meet him and talk with him about what it was actually like to go through all those things, and ask him a million questions. He made himself available to all of us to answer any question that we could come up with. So it was a daunting prospect, but really, really fun in the doing of it.

I was going to ask you if you had spoken to him. What were those conversations like, and what questions did you have for him?

Oh, gosh. Well, we got to spend at least 12 or 13 hours together in his law offices. Then he brought me to his house to meet his family, we took a long walk in the park and we had lunch together. I asked as many questions as I could. It was fantastic. It’s rare to get the opportunity to talk to the people that you’re going to be playing. But he was an open book, and he was really sweet about the whole thing. I think primarily he was interested in making sure that how a criminal defense lawyer is portrayed may be done so in our project as above board as possible. He takes his work very seriously and he’s really good at it. So I think it was important for him, for myself and for all of us to help show what criminal defense lawyers do in the best possible light.

What were your main inquiries for the real David, in terms of what you needed for your acting?

That’s an excellent question. I didn’t know what I needed. It’s just an opportunity to be with an individual who lived through something or made something happen. I wanted to know a lot about who he was before all this took place, and what brought him there. About his schooling, his family, his relationships — what it was that got him jazzed about being a lawyer in the first place. What kind of a human being he is or was, and why it is that he thrives doing what he does. Even now, I was particularly interested to learn about how his life changed during the course of this particular trial and how it really sent his life in a different direction. He and his wife go about trying to help people who’ve been wrongly accused, and I’m glad to know that they’re spending their time doing that.

Something I was wondering from watching both the documentary and the new series is why David agreed to the documentary crew’s request to film. I’m curious what your answer is for that, and whether you were able to speak with the real David about that.

I was, and he explained to me that it was neither here nor there with him, because he was still going to go about doing his job. But he said, “Look, here are my rules that you need to follow.” He didn’t think they would agree to them, frankly, because most documentarians probably wouldn’t have. They did agree to it, obviously, otherwise we wouldn’t be here. In the end, I don’t know how much it necessarily changed who he was or how he defended his client, but he probably would have done the same thing if he had the opportunity to do it again. He would probably do it under those circumstances as long as it didn’t harm his client. He was fine with it all.

Throughout the trial in Episode 4, we really get to see David start to become more critical of Michael. I’m curious how you approached David’s internal life as he was dealing with that.

Anything that’s going to make David’s case more difficult in terms of information not being revealed by his client was something that I imagine just made him angry. You know, “Look, I’m trying to help you here. You have to give me everything you can so I can help you. I’m not judging you about your life or anything. The more I know, the stronger our case is going to be because we won’t be able to be surprised by the prosecution. So give me everything.” There were certain frustrations when things kept being revealed and there was nothing David could do about it.

At the same time, you have to make do with what happens, and I imagine how frustrating that might be if you’re trying to help somebody and they’re the one who’s not giving you all the help that they could. It was interesting trying to navigate those things. All that someone trying to walk in his shoes can do is offer up as many different options to the filmmaker as possible in terms of how one might react under certain circumstances. Then it’s up to them to include whichever they think is the best version.

Did playing this role give you a different perspective on the real Michael? Because I’d imagine that you have to look at it from a completely different angle when you’re on his defense.

Maybe I paid attention to the coverage that I was privy to of Michael in a more focused manner than I did before, as opposed to just letting it wash over me. I don’t know if it changed my opinion of him. In the end, it’s Colin and I engaging in whatever the moment happens to be. So I’m taking in what I’m given as opposed to something that’s not in front of me. So I’m reacting immediately to the circumstances, which is Colin. So it’s going to be different from how I would react if I met the real Michael Peterson.

What was that like working with Colin, and what was that dynamic like between the two of you, since you seem to have most of your scenes together?

Wonderful. Everything you’d want it to be. He’s so smart and accomplished. I learned a lot about what it is we do and trying to tell a story in this medium. He’s got a great sense of humor, and I really enjoyed my time with him. It was really fun to watch him navigate what he had to go through emotionally and intellectually and to see all the different choices he made, and the way he went about trying to achieve those.

In this show, is there anything that was specifically a challenge for you?

I remember feeling a great sense of wanting to honor what it was I had seen in regards to the documentary, because I watched an awful lot and in some cases we were recreating those moments. So I felt a great sense of wanting to honor what I had seen as truly as I could, but not giving the exact same words because our writers didn’t want to use the same words. It wasn’t like we were trying to create the same thing. What would be the point of that? So we were showing it from a different point of view. I wanted to honor those things, and bring along with me the ramifications of what would happen if I wasn’t able to do what it was I was being tasked to do. In other words, trying to get Michael off in the circumstances and then trying to bring with me what that feels like. What are the stakes under these circumstances? If I can’t get Michael out of prison, or trying to feel what it must have felt like to expect a certain outcome and then have it flip on you like that. Trying to make those instances real for me. He had something that he really wanted to do. And I think the most difficult part was trying to take the information that I had learned and try to make it real for myself as much as possible.

At this point, having done the show, do you have any of your own theories?

Well, I haven’t come up with anything new, honestly. I’ve taken all the information that I’ve been privy to, and there are some that make more sense to me than others. Honestly, in terms of the logic, it just seems like certain things happened and the facts that we’re left with logically unfold in a particular way. You know, the whole owl theory circumstance and all that stuff, that gets explored, as well. There’s a lot of smart people who’ve applied themselves to this story, and it’s great that we’ve gotten to explore it a little bit in several, several different ways.

This interview has been edited and condensed.