Several years ago a small publishing house called Moon Rock Books published a 455-page volume that argued the Sandy Hook Elementary School massacre had never happened.

In a dozen chapters, the book professed, among other things, that the school had been abandoned years before a gunman killed 20 first graders and six staff members.

The Federal Emergency Management Agency, it claimed, had staged the event in Connecticut to promote gun control measures.

And Leonard Pozner, the father of the youngest child to die that day, had faked his 6-year-old son’s death certificate in service of the conspiracy, it claimed.

On Monday, Mr Pozner, who has made it his life’s work to stop those who would seek to deny the 14 December 2012 school shooting, won a key challenge.

Heroic Sandy Hook staff saved many lives as the killer struck Show all 9 1 /9 Heroic Sandy Hook staff saved many lives as the killer struck Heroic Sandy Hook staff saved many lives as the killer struck AN13475677Victoria-Soto-27-.jpg Victoria Soto

Victoria’s cousin, Jim Wiltsie, a police officer, said the 27‑year‑old died trying to shield her pupils. “I’m just proud that Vicki had the instincts to protect her kids from harm,” he said. “It brings peace to know that Vicki was doing what she loved, protecting the children, and in our eyes she’s a hero.” REUTERS Heroic Sandy Hook staff saved many lives as the killer struck 04-heroicstaff2.jpg Heroic Sandy Hook staff saved many lives as the killer struck 04-heroicstaff3-AP.jpg AP Heroic Sandy Hook staff saved many lives as the killer struck 04-heroicstaff4.jpg Heroic Sandy Hook staff saved many lives as the killer struck 04-heroicstaff5.jpg Heroic Sandy Hook staff saved many lives as the killer struck 04-heroicstaff6.jpg Heroic Sandy Hook staff saved many lives as the killer struck 04-heroicstaff7.jpg Heroic Sandy Hook staff saved many lives as the killer struck 04-heroicstaff8.jpg Heroic Sandy Hook staff saved many lives as the killer struck 04-heroicstaff9.jpg

A judge ruled for the first time that Mr Pozner had been defamed by the publication of Nobody Died At Sandy Hook: It was a FEMA Drill to Promote Gun Control.

“This is a victory for myself and my family,” Mr Pozner said in an interview on Tuesday.

“It is also a victory for the survivors and victims’ families of all mass casualty events who have been targeted by these people.”

The advocacy of the group Mr Pozner founded, the HONR Network, has helped push corporations, like YouTube and Facebook, to remove thousands of false posts about the massacre, and to provide new ways for users to report hateful content.

Other family members of victims and survivors of the attack have also been involved in recent years in taking on conspiracy theorists on a variety of fronts, including through legal action.

Judge Frank Remington of Dane County Circuit Court in Wisconsin ruled on Monday that the co-editors of the book, James Fetzer and Mike Palecek, had defamed Mr Pozner in their book by alleging multiple times that he had faked his son’s death certificate to promote the conspiracy. The case will now go to a jury to determine damages.

The book’s publisher, Dave Gahary of Moon Rock Books, also agreed to stop selling the book as of 30 June in a separate settlement. He said that after meeting Mr Pozner in May and hearing his story for himself, he now believes him.

“My face-to-face interactions with Mr Pozner have led me to believe that Mr Pozner is telling the truth about the death of his son,” Mr Gahary said. “I extend my most heartfelt and sincere apology to the Pozner family.”

The ongoing battle by the families of Sandy Hook victims to stop disinformation about the attack shows how persistent conspiracy theories about the massacre remain nearly seven years after one of the deadliest mass shootings in US history.

Mr Pozner is also suing Alex Jones, the right-wing conspiracy theorist and founder of Infowars, over his assertions that the massacre was an elaborately staged ruse meant to promote gun control. That case is proceeding in Texas.

Separately, another case against Mr Jones brought by relatives of five children and three adults killed in the shooting, along with one FBI agent who responded to the scene, is proceeding in Connecticut.

Six year anniversary since deadly shooting at Sandy Hook elementary school

In 2016, a Florida woman, Lucy Richards, was sentenced to five months in prison for sending Mr Pozner death threats. She was also banned from visiting websites run by conspiracy theorists, including Mr Fetzer’s.

On Monday, lawyers said in court documents in the Connecticut case that Jones’ legal team had included an image of child pornography as part of his legal filings in that case. Mr Jones denied the allegation, calling it an attempt to frame him.

The legal challenge in Wisconsin focused on Mr Fetzer, a retired professor at the University of Minnesota Duluth, who lives in Dane County, Wisconsin, and has been asserting for years that the Sandy Hook killings were staged.

Along with his co-editor, Mr Fetzer has also advanced conspiracy theories about the 9/11 attacks, John F Kennedy’s assassination and other events.

He is alleged to have zeroed in on Mr Pozner as being involved in the conspiracy, leading the former professor to experience harassment and threats.

To prove the case, Mr Pozner’s legal team provided a certified copy of Noah’s death certificate, as well as DNA evidence from the Connecticut medical examiner showing that he was Noah’s father, said his lawyer, Jake Zimmerman.

Judge Remington said there was no question of fact in dispute, and ruled in favour of Mr Pozner in the libel case, allowing it to proceed to a jury to consider a penalty.

Mr Fetzer and Mr Palecek are representing themselves in the lawsuit. Mr Fetzer, in an email, restated his belief that Noah’s death certificate was faked.

“The American people are entitled to know the truth about their own history,” he said.

Mr Pozner, 51, said he lives in hiding because of ongoing harassment by Sandy Hook hoaxers. Noah was also survived by his mother, Veronique De La Rosa, a twin sister, Arielle, now 13, and an older sister, Sophia, 14.

Mr Pozner had also sued the book’s publisher, Moon Rock Books, which is part of a broader company, Wrongs Without Wremedies LLC.

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But its principal officer, Mr Gahary, said on Tuesday that after listening to Mr Pozner’s 15-hour deposition, he no longer had any doubt that he had truly lost his son.

“I came away from that believing that he was telling the truth,” Mr Gahary said in an interview. “And I felt personally bad for anything that I had done to contribute to his misery.”

Mr Gahary, who has published multiple conspiracy volumes, said that he has been swamped with hate mail since his change of heart became public, including from Sandy Hook deniers who have accused him of betrayal. He said he hoped to send them a message.

“If someone like me is saying that I believe him,” he said, “it should carry some weight, and they should look at this event differently.”