Warning: This article contains spoilers for all 13 episodes of The Staircase on Netflix.

Landing on Netflix last month, The Staircase has become the internet's latest true-crime obsession, with debate raging across websites, blogs and social media about the owl theory, the blow-poke, and, of course, whether or not the series' subject is innocent or guilty.

The 13-part documentary tells the story of Michael Peterson, a novelist living in Durham, North Carolina, who was put on trial for the murder of his wife Kathleen. Peterson insists that Kathleen fell down the staircase in their home, but ends up spending eight years in jail, despite the best efforts of his lawyer David Rudolf.

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After a long spell behind bars, blood-spatter analyst Duane Deaver – whose testimony was crucial in convincing the jury to put Peterson away – ends up discredited after his questionable practices are exposed.

But rather than face another lengthy retrial, one which could still land him back in jail, Peterson ultimately decides to take an 'Alford plea' – in which a defendant does not actually admit guilt, but still pleads guilty, in the acknowledgement that the evidence is substantial enough for a conviction (whatever the truth may be).

Now, in a candid new interview with Digital Spy, Rudolf – Michael's attorney, on-and-off, for 16 years – opens up about his frustrations with Peterson's original trial, his feelings towards Kathleen's sister Candace Zamperini and his difficult experience with Microsoft Powerpoint.

Clearly, the whole experience documented in The Staircase was a deeply emotional one for you. What made you finally decide, in 2014, to take a step back from Michael's case?

"Well, you know, up to that point, I had been trying to resolve the case. [But] I really did not want to go through another four- or five-month trial.

I just realised I was emotionally spent, that I could not go back and retry this case again and be as effective as I was the first time. That's when I reached out to a younger lawyer who I felt would be very good, and put Mike Peterson in touch with Mike Klinkosum."

Looking back, do you regret that decision to step back?

"I can't regret it, because it was not really a choice for me. For me, it was an essential decision. And I'm glad I was able to step back in later on and bring the case to closure. But at the time, in 2014, when it really looked like it was going to be retried, that just wasn't an option for me."

Speaking of closure, are you satisfied with how the whole saga ended – with Michael taking the Alford plea? Or is there a part of you that wishes you could have got that "not guilty" verdict in court?

"Well, the ego part of me wishes I could have gotten the 'not guilty' in court at the end of the day. But from a professional perspective and from – more importantly – a client's perspective, it was the right thing to do.

"So am I satisfied with it? I can't say that I'm satisfied with it. I'm comfortable with it. I think it was the right thing to do. I know that, for Michael, it was the right thing to do. But there's a part of me that is a little bit ambivalent about not going back and getting to hear a jury say 'not guilty'."

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How confident are you that you would have got that "not guilty" verdict had the case gone to a retrial?

"Well, I was confident the first time, so… [ laughs ] My confidence in what would happen in that case is shaken.

"Assuming that the Germany stuff [Editor's note: Peterson's close friend Elizabeth Ratliff was also found dead at the bottom of a staircase at her home in Germany, after suffering a cerebral haemorrhage] would have been out – and the judge indicated that it would not have been admissible, and it never should have been admissible – and if the bisexuality evidence was out, and it was never relevant, and should have been out from the beginning...

"And, of course, Deaver was all over the 'crime scene', which is what they called it. So you know, I think the prosecution would have been hard-pressed to prove guilt beyond a reasonable doubt. But who knows?"

Related: The Staircase raises an all-important question for true-crime fans

How did you feel about Judge Hudson's comments that he regrets allowing certain things – such as the bisexuality – into evidence?

"Well, again, I was ambivalent. I thought he displayed great courage in saying that. Most judges probably wouldn't have admitted that. So I think it's to his credit that he was willing to not just say it, but to say it on camera, where it matters even more.

"On the other hand, I think those were decisions that should have been reached 15 or 17 years ago now. If they had been, you and I might not be speaking today."

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The reveal of Michael's bisexuality seemed to colour the jury's opinion of him. Do you think now, in 2018, that revelation would have such an impact?

"Well, I certainly think the world has changed in a great many ways, and particularly with regard to the issue of sexuality, and bisexuality, and homosexuality. So I don't know how it would play.

"I don't know if the prosecutor would even try to present that evidence in 2018. It might very well backfire in 2018 – that kind of approach by the prosecution might have alienated jurors. But had a prosecutor done that in 2018, I think it would have had less impact."

Michael being found guilty in his first trial was clearly a huge emotional blow for you – has everything that's happened since healed some of that damage?

"It's healed some of the damage. What was a great relief to me personally was obtaining that new trial in 2011 – vacating that conviction. That was something that took a tremendous weight off of my shoulders.

"So yeah, that went a long way towards healing me. But of course, I still don't really understand how a jury found Michael guilty to begin with. To the extent that the original verdict shook my faith in understanding jurors, I think that that's still there."

How serious a problem do you think "junk science" is in the criminal justice system?

"I think it's a very serious problem. I think that there's a lot of quote-unquote 'science' that is not really evidence based, that is not peer reviewed, that is not subject to testing and confirmation.

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"There was a very lengthy report on all of this done by the Justice Department in the United States back in 2007 or 2009, I think. It pointed out that, with regards to things like blood spatter and hair analysis and even fingerprinting, there are no standards. Whatever anybody says is a match is [considered] a match.

"It's very subjective, in other words. I think we really have to be careful with what we call science in the courtroom."

You allowed The Staircase filmmaker Jean-Xavier de Lestrade and his team unprecedented access to your working process. Did you ever regret that decision?

"No. I really never did. I struggled with the decision right at the start, and it was very important to me that nothing would be broadcast until this case was over. But once I knew that, I never really struggled with the decision to do it.

"The filmmakers were very respectful. They never asked me to redo something. They were simply flies on the wall. They stayed in the background, and they really didn't affect anything that I was doing.

"Now, they didn't film every single moment of my life, and they certainly didn't film every conversation that I had with Michael – or other people, for that matter. But what they did film and what they presented in the film is a fair representation, an accurate representation of what we were doing in getting ready for the trial.

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"There was never a time when I refused to let them film something. There were times when they simply weren't around, and I wasn't about to schedule things around their convenience.

"But there was never a time when, for example, a meeting started, and at some point I said, 'Listen, guys, you need to leave. I can't have this filmed'. That just never happened."

Jean-Xavier suggested that the prosecution in Michael's first trial couldn't prove that he was guilty, so they tried to prove that he was "the kind of person who may have killed his wife" – do you think that's a fair assessment?

"I think that is a completely accurate assessment. There was no evidence of motive that ever stood up to cross examination. They started off trying to prove a financial motive. That was completely undermined by the cross examination of their financial expert, and the fact that during the time [the Petersons] were allegedly under financial stress, Kathleen was deferring her salary into a bank account. I mean, literally, not taking a large portion of her salary so that it could be saved for the future.

"The other motive, which was allegedly that Kathleen found some email correspondence on Michael's computer on the night of the death [revealing his extra-marital affairs], was undermined by the cross examination of their own computer expert, who testified that there was no evidence that she ever accessed Michael's computer after the call with her co-worker, which was completely normal.

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"So there was no motive. There was no murder weapon. The whole thing inconsistent with the way that they had lived their life, and it was inconsistent with what they were doing that night, which was drinking wine and watching a movie at 10 o'clock at night, as confirmed by an independent witness – a doctor who happened to visit the house with [Michael's son] Todd at about 10pm that night.

"Given all that, what they were left with was: a) trying to tarnish Michael's character, and b) relying on this death in Germany, which there was absolutely no evidence Michael had anything to do with. It really became a character assassination."

The very final episode of The Staircase is an incredibly powerful watch. How did it feel to be sat in court when Candace gave her final speech?

"Well, I would actually call it a diatribe. We can call it 'a speech' if you'd like!

"What was that like? I sat there and I was sort of waiting my turn [ laughs ]. I sort of knew at some point she was going to turn her ire on me!

"All I could do was sit there and tell myself that it's really sad that she is so consumed by anger and hatred. So it really wasn't hard for me to just sit there and not react, because the truth is, I felt sorry for her. That's mostly what I felt."

How do you feel about people making light of certain aspects of The Staircase, like your frustration with the PowerPoint presentation?

[L aughs ] "At the time, it wasn't funny to me at all – as you can tell. In retrospect, you know, watching that particular sequence, and then when the sheriff comes in to tell me there's a fire in the building, and meanwhile, my patience with the IT operator is about nearing its end... it's almost an Abbott and Costello routine.

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"So I can look back on it with a different perspective now, and I can understand why people think it's humorous. And in retrospect, it probably is pretty humorous!"

The Staircase arriving on Netflix has generated all kinds of new discussion about the case. How plugged into all of that have you been?

"I've been fairly active in that, and the reason is not because I care very much about what people think about guilt or innocence. People can reach their own judgements about that, people can reach their own judgements about the explanation for the wounds on her scalp – [whether it was] an owl's talons, or something else.

"What I care about, and the reason I've remained engaged, is about the light that the series casts on the criminal justice system, and the issues that exist – not just in this case, but in many, many cases.

"So I want to stay involved in that discussion, and I want to continue to bring light to that topic. If I'm invited to speak at various places, I want to talk about that. I'm sure people will have a question about the owl theory here and there. But I really hope that I can keep my focus on the larger issues that I think are really well-presented in this documentary.

"That's really what the documentary was meant to explore – how the criminal justice system in the United States works, or does not work. And that's what I'd like to remain focused on."

The Staircase is streaming now on Netflix.

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