Conspiracy theorist Alex Jones has been ordered to pay $US4.1m ($NZ6.5m) in damages after falsely claiming the Sandy Hook school shooting in 2012 was a hoax.
Parents of the victims had been seeking at least $US150m ($NZ238m) in the defamation trial against the Infowars host.
They said they had endured harassment and emotional distress because of Jones' misinformation.
The shooting at Sandy Hook elementary school left 20 children and six adults dead in Connecticut in 2012.
The jury in Austin, Texas, decided compensatory damages on Thursday, and must still determine any punitive damages.
Jones repeatedly argued that the shooting was a hoax organised by the US government to strip Americans of gun ownership rights, and that the parents of the dead children were actors.
He has already lost a series of defamation cases brought by parents of the victims by default after failing to produce documents and testimony.
This is the first case in which damages were determined by a jury.
Ahead of the decision, lawyers for the two parents who brought the lawsuit - Scarlett Lewis and Neil Heslin - revealed that Jones' lawyer had inadvertently sent two years of text messages from his client's phone.
The messages could be of interest to the congressional panel investigating last year's US Capitol riot. The committee said Jones helped organise a rally that took place just before the riot.
Despite retracting his claims about Sandy Hook, Jones has continued to use his platform to attack jurors and the judge in this case.
He also claimed he was bankrupt despite evidence that his companies were earning about $800,000 dollars a day selling diet supplements, gun paraphernalia and survivalist equipment.
During the emotionally charged trial, Jones portrayed the case as an attack on his free speech rights under the First Amendment of the US Constitution.
"Speech is free, but lies you have to pay for," lawyers for the families countered in their opening arguments.
Jones also conceded the killings were "100 percent real" and accused the media of not allowing him to retract his false claim.
In her testimony, Lewis addressed Jones directly in court, saying: "Jesse was real, I'm a real mom."
She went on to say it was "incredible to me that we have to do this".
"That we have to implore you - not just implore you, punish you - to get you to stop lying," she continued, adding: "It is surreal what is going on in here."
Heslin said Jones' lies "tarnished the honour and legacy" of his son, adding that he had gone through nearly 10 years of "hell" since the attack.
According to lawyers for the parents, they hired private security for the trial out of concern that followers of Jones could seek to harm them.
- BBC