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Today The Staircase, a very good true-crime documentary that originally debuted as a French television miniseries in 2004, comes to Netflix. I first saw the documentary in 2012, after Mindy Kaling raved about it on Marc Maron’s WTF podcast. At that time, if you wanted to watch The Staircase, you had to order the DVD set online. (This is just me wanting you to give me credit for knowing about The Staircase before you did.) (But after Mindy Kaling did.) Anyway, it’s a great series, and you should definitely watch it, and you should also come to the same conclusion I did, which is the same conclusion I come to at the end of most true-crime phenomena I absorb: he totally fuckin’ did it.

In this case, as with most of the true-crime cases that have been spun into popular TV series, the judge and jury agreed with me: Michael Peterson was sentenced to life in prison for the murder of his wife, Kathleen, though he was released on an Alford plea — in which the convicted party maintains his innocence, but acknowledges that the evidence presented would likely persuade a jury of his guilt, in order to receive a lesser sentence — last year. (Netflix’s version will include three new episodes, all filmed in 2016.) But Peterson’s guilt is contested, and not just by his defense team — no spoilers, but just wait until you hear about the owl theory. The evidence is not incontrovertible. There are certain questions left unanswered. And yet, I am positive. Why? Because Michael Peterson just … seems guilty.

Hoping to get validated for my correct opinion, I spoke to N.G. Berrill, executive director of The New York Center for Neuropsychology and Forensic Behavioral Science. After a brief description of the documentary, which certainly did not do it justice (ha), I told Berrill why I’m sure Peterson did it. Unfortunately, he did not seem to find me a brilliant, uniquely capable judge of character he’d like to hire immediately as a consulting detective. “I think we all work on the basis of the belief that we may have some talent at discerning who’s a liar or who’s guilty of something,” says Berrill. Bad news: we’re not as talented as we think. Even someone like Berrill, who has years of experience working with criminal offenders, can’t necessarily tell if someone’s lying when they say they didn’t do it. “I sometimes walk out of a room saying ‘this guy’s full of crap, it’s just obvious,’ and then he’ll pass the polygraph,” he says. (The accuracy of polygraphs themselves is controversial, too; though it’s an imperfect tool, Berrill says it can be helpful in discouraging his patients from lying, simply because they know they’ll be tested regularly.)

Okay, sure. But Michael Peterson is just so weird. There are little things, like the pipe smoking, and bigger ones, like the disaffected manner in which he recounts the night his wife died. And his tone of voice in the 911 call sounds totally put on, almost theatrically fake. I just don’t trust him. Doesn’t that count for anything?

Well, no, says Berrill. Even if I think I’m judging Peterson on his own merits, I’m not, because unbiased judgment is impossible. “We all have conscious and subconscious concerns and biases toward individuals who we meet,” says Berrill. “They may remind of us of someone we know, who we particularly like or don’t like. That informs how we receive the information that we’re getting from this person.” If I had a friend who looked like Peterson, says Berrill, I’d probably be more likely to give him the benefit of the doubt without even realizing I was doing it. The opposite holds true if I had an enemy who looked like him. And then there are more systemic, pernicious forms of prejudice, like racism and classism, which have been proven to affect juries’ perceptions of defendants’ guilt. Michael Peterson is a white man, and at the time of his arraignment, at least, he was a wealthy one, too. These are not marginalized identities, but they almost certainly play a role in my assessment, however subconsciously.

In fact, I’m sure they do, because the other reason I’m convinced Michael Peterson killed his wife is that, more often than not, when a woman is killed, her boyfriend or husband (or ex) is the one who did it. Here, at last, Berrill concedes I’m right about something. But being right about statistical likelihood is not the same as being right about the individual; it’s just another form of bias.

The essential fact remains that if we weren’t present for the crime, there’s a lot we just can’t know. Part of the reason we assign guilt based on “strange” post-crime behavior like Peterson’s scripted-sounding 911 call, or his first tear-less statement to the press, is because we think we know what we’d do in the same situation, says Berrill. “We put ourselves in their shoes and say, well if it was me, I would be crying hysterically, or I would be frantic,” he says. “What you would do in a situation or think others would do doesn’t always happen to be the case.” For instance, Berrill tells me people often say they’re suspicious of suspects who are “too cool” in the face of interrogation, but some people are just like that, just like some people are obnoxious and weird. A bad personality, and even a criminal history, does not sufficiently indicate guilt, says Berrill. There is, in fact, no way to tell for sure if someone is guilty by observing or talking to him alone. In fact, there’s only one reasonably reliable criteria Berill comes back to.

“If somebody has a long history of lying, and being caught in their lies, that’s a good sign that you might be dealing with a liar,” says Berrill. But even then, you may never know for sure, which is part of what makes these series so compelling. You can feel superior to the jury members, and certain you know the truth, but ultimately, you are at home, on the couch, far away from the courtroom — an unskilled observer, no matter how many true-crime documentaries you’ve watched.