Every true-crime fan more or less has an opinion on the case of Kathleen and Michael Peterson. The Staircase, a 13-episode documentary by Oscar-winning director Jean-Xavier de Lestrade and HBO Max's latest true-crime drama of the same name have helped make the case known across the world.

In 2003, Michael Peterson was convicted of killing his wife Kathleen Peterson after she was found dead in a pool of blood at the bottom of the staircase in their home on December 9, 2001.

He was released in 2011 pending a retrial but in 2017 he submitted an Alford plea to the lesser charge of voluntary manslaughter meaning he accepted there was enough evidence to be convicted but he was able to maintain his innocence. He was sentenced to time already served and was released from prison.

At Peterson's 2003 trial, the defense argued Kathleen died after falling down the stairs and there was no motive for Michael Peterson to kill his wife. The defense stated Kathleen and Michael had a happy marriage and that she was accepting of his bisexuality.

On the other hand, the prosecution successfully argued Michael murdered Kathleen after she found out he was having affairs with men. There was also Kathleen's $1.5 million life insurance policy to think about.

No doubt at the 2003 trial and most definitely after Michael was sentenced to life in prison without parole for the murder of his wife, followers of the case had their own thoughts and theories on what happened the night Kathleen died and many more still do to this day.

Numerous theories have surfaced over the years but the most prominent of them all was "The Owl Theory" which was conceived by Michael's neighbor, Lawrence Pollard in 2008.

The Owl Theory argues Kathleen died from blood loss after being attacked by an owl and was not killed by Michael.

Speaking to Newsweek, Michael's lawyer David Rudolf shared he and his client did not buy the theory when they first heard about it.

He shared: "It's something that I dismissed at first, as did most people because there really wasn't any substance to it, other than the fact that Larry Pollard believed it and the scalp wounds were certainly reminiscent of a talon, which is what caused him to even think about the theory."

Pollard believed Kathleen may have been attacked by a barred owl outside her home, fallen down after rushing inside, and fallen again on the stairs, knocking herself unconscious. She then bled out from her injuries.

Pollard believed the head injuries were caused by the sharp talons of an owl, not a blunt object like a fire poker as argued by the prosecution at the trial.

His theory was strengthened when he discovered the evidence collected by the North Carolina State Bureau of Investigation (SBI) included a microscopic owl feather and a wooden sliver from a tree limb. These were discovered in a clump of Kathleen Peterson's hair that had been pulled from her head and that she was holding in her left hand when she was found.

A further re-examination of the evidence found that there were not one, but three microscopic owl feathers discovered on her body.

The Owl Theory was not put forward at Michael's trial back in 2003 as his legal team was unaware of it, Rudolf explained to Newsweek, adding: "It's not something that I considered at that moment."

In 2010, the view of medical examiner Deborah Radisch (who carried out Kathleen's autopsy) that an owl or any other bird would not leave wounds as deep as the ones found on Kathleen's scalp was challenged by experts in three individual affidavits in 2010, reported The Durham News.

The experts were Dr. Patrick T Redig, professor of veterinary medicine at the University of Minnesota, neurosurgeon, owl expert and former U.S. Navy surgeon Dr. Alan van Norman and director of Raptors of the Rockies, Kate P Davis.

Despite growing belief in the Owl Theory, no motion for a new trial was filed based directly on the evidence supporting it.

Rudolf admitted that over time, he has come to realize the Owl Theory is more "believable" than he first thought.

What persuaded Rudolf was the fact there have been hundreds, if not thousands, of documented accounts where owls have attacked the heads of their victims. There are also barred owls living in the woods by the Peterson's former home in Durham, North Carolina.

The injuries to Kathleen's head also mirrored the marks of an owl's talon.

Rudolf shared: "Over time, as [Pollard] contacted experts, as he got opinions from experts, as we started to hear about owl attacks on other people, and then of course, once Google sort of got started, and you were able to get on Google and type in 'barred owls attacking humans,' and you'd have at first 10, and then 50, and then 100 different stories from various places in the world. You'd have pictures, you'd have video, it became much more believable."

Rudolf shared Michael also came round to accepting the Owl Theory as a possible explanation for what happened to his wife.

He said: "He [Peterson] was like the rest of us. I think he dismissed it at first but again, I think like with me, gradually over time, you start to take it a little bit more seriously, given all the other information that exists. In fact, there's evidence at the scene that tends to support it and there's certainly nothing that I'm aware of that refutes it, or makes it impossible."

Today, Peterson is a free man but with the HBO Max series and the interest in the Netflix documentary, true-crime enthusiasts are sure to be debating the Owl Theory for weeks to come.

The Staircase airs Thursdays on HBO Max and Sky Atlantic.

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