Making a Murderer made me public enemy number one, claims Wisconsin Deputy District Attorney Michael Griesbach

Now is not a pleasant time to be a public official in Manitowoc County.

Since Netflix released its 10-part, true-crime series Making a Murderer in mid-December, police and prosecutors in the rural Midwestern community in Wisconsin have faced petitions, demonstrations and death threats from those who believe they wrongly convicted a local man called Steven Avery not once, but twice.

“It’s weird being here,” said Deputy District Attorney Michael Griesbach. “Last Friday there was a demonstration at the courthouse: about 80 people from all over the country yelling ‘Free Steven Avery’. There have been threats on Facebook directed at me and at the District Attorney, who wasn’t even here at the time of Avery’s trial.”

Avery, now 53, spent 18 years in prison for a 1985 sexual assault before being exonerated by DNA evidence in 2003. Two years later, on the verge of winning a $36m (£25m) lawsuit against Manitowoc County for wrongful conviction, he was arrested – and then convicted again – for the murder of 25-year-old photographer Teresa Halbach.

Avery’s lawyers claimed he had been framed by police for a second time, a case Making a Murderer outlines in compelling detail. So compelling, that hundreds of thousands of viewers signed a petition demanding a pardon. Ken Kratz, the DA from nearby Calumet County who led the prosecution, has had death threats, as have the police officers scrutinised at the trial.

Mr Kratz is reportedly writing a memoir to present his side of the story, but his will not be the first book about the case. Mr Griesbach’s The Innocent Killer, which explores the 1985 and 2005 cases in detail, was published in the UK for the first time this week. Mr Griesbach was instrumental in Avery’s 2003 release, but also believes he is guilty of Ms Halbach’s murder.

“I really do think he got a fair trial,” he said. For arguing as much in public, Mr Griesbach has had his Facebook page “hijacked” by fans of the series. “It’s irrational,” he said. “No matter what you say ... what facts you present, nothing will convince them they’re mistaken.”

Mr Griesbach moved to Manitowoc in 1991, by which time Avery had been incarcerated for six years for the assault on local woman Penny Beernsten. When DNA proved another man was responsible, Mr Griesbach investigated the original case, later testifying against his own colleagues in Avery’s lawsuit.

It was clear, he said, that “it went way beyond a mistake or over-zealousness on the part of the police. The former DA [Denis Vogel] and former sheriff [Tom Kocourek] either knew he didn’t do it within a few days of arresting him, or they should have known, but recklessly disregarded the evidence. It was pretty ugly.”

Yet, Mr Griesbach insists, the corrupted criminal justice culture of Manitowoc County has “completely flipped around” since. A “different era started shortly before Avery was exonerated in 2003. People in the police department now are disgusted by what Vogel and Koucerek did.”

When Avery was arrested for the Halbach murder, in the midst of his lawsuit against the county, the Manitowoc DA handed the case to Mr Kratz and Calumet County, to avoid a conflict of interest. Mr Kratz was glad to have it. “Kratz loved the media,” Mr Griesbach said. “In my first, self-published, version of the book I called him Ken ‘I never saw a camera I didn’t like’ Kratz.”

The Manitowoc County Sheriff’s Department was not so conscientious, as the documentary explains, and its officers continued their investigation despite the conflict of interest. At the trial, two – Lt James Lenk and Sgt Andrew Colburn – were all but accused outright of planting evidence pointing to Avery’s guilt.

Contrary to the insinuations of Making a Murderer, Mr Griesbach calls Lenk and Colburn “two of the most ethical cops I’ve ever worked with”. He added: “I can see why people think evidence was planted, but I don’t believe they did it. Should they have been searching Steven Avery’s home? Absolutely not. But I don’t think it was malice on their part, I think it was just poor judgement.”

True crime is undoubtedly the genre of the moment. Robert Durst, real-estate heir and subject of a recent HBO documentary series, The Jinx, pleaded guilty to gun charges in New Orleans this week, and may be extradited to Los Angeles to face trial for the murder of his friend Susan Berman in 2000. Adnan Syed, convicted of the murder of his high-school girlfriend Hae Min Lee in the same year, was in court in Baltimore on Wednesday, to argue for a fresh trial for the first time since his case was examined by the hit podcast Serial. A series recreating the 1995 OJ Simpson trial, The People v OJ Simpson, premiered on US TV on Tuesday.

“The line where entertainment meets reality is blurring,” Mr Griesbach said. When he began writing his book, first published in the US in 2014, the Halbach family weren’t happy, he admitted. But, he added, his book does start “a useful discussion about the criminal justice system”.

Mr Griesbach sits on the Wisconsin Innocence Project board, with Avery lawyers Dean Strang and Stephen Glynn, and Ms Beernsten, who wrote an afterword to The Innocent Killer. Insisting he is “not just a spokesman” for the cops and prosecutors of Manitowoc County, he described Making a Murderer as “one-sided” and “agenda-driven”.

“One thing I agree with the documentarians about is that truth is elusive in the Steven Avery case,” MrGriesbach said. “But what rings out most strongly for me is that Steven Avery, regardless of where or who he did it with, killed Teresa Halbach.”