A US jury has awarded $450,000 (£350,000) to the father of a boy killed in the 2012 shooting at Sandy Hook school, in a defamation lawsuit against a conspiracy theorist writer.

In June a Wisconsin judge ruled that James Fetzer had defamed Leonard Pozner by claiming he had fabricated the death certificate of his son Noah.

Mr Fetzer, who co-wrote Nobody Died at Sandy Hook, said he would appeal.

Noah, aged six, was the youngest of 26 people killed in the shooting.

In the Dane County court in Wisconsin, Mr Pozner thanked the jury for recognising “the pain and terror that Mr Fetzer has purposefully inflicted on me and on other victims of these horrific mass casualty events, like the Sandy Hook shooting”.

In his book, written with co-author Mike Palacek, Mr Fetzer claimed that the Sandy Hook shooting was a hoax, manufactured by the Obama administration as part of an effort to tighten gun laws.

The book, and a later blog post by Mr Fetzer, included several false statements about Noah’s death certificate, including claims that Mr Pozner had circulated fabricated copies.

Mr Pozner reached a settlement with Mr Palacek last month. The terms have not been disclosed.

On Tuesday, Mr Pozner emphasised that the case was not about First Amendment protections for free speech.

“Mr Fetzer has the right to believe that Sandy Hook never happened. He has the right to express his ignorance,” he said, according to the Wisconsin State Journal.

“This award, however, further illustrates the difference between the right of people like Mr Fetzer to be wrong and the right of victims like myself and my child to be free from defamation, free from harassment and free from the intentional infliction of terror.”

Mr Pozner’s lawyer Genevieve Zimmerman described Mr Fetzer’s claims in both the 2015 book and 2018 blog post as “alt-right opium”.

It is one of several defamation cases launched in the wake of Sandy Hook, many led by Mr Pozner.

He and Noah’s mother, Veronique De La Rosa, have also sued prominent conspiracy theorist Alex Jones for defamation. The pending case is one of at least five faced by Mr Jones.

Last week, a Texas court ruled that Mr Jones could not invoke free-speech law to end a separate suit, waged by Scarlett Lewis, the mother of Sandy Hook victim Jesse Lewis.

Parents of Sandy Hook victims who have spoken publicly about their experiences have been targeted by trolls, both online, as well as in person.