Conspiracy theorist Alex Jones repeatedly “lied and attacked the parents of murdered children” when he told his Infowars audience that the Sandy Hook elementary school shooting was a hoax, an attorney for one of the victim’s parents told a Texas jury on Tuesday at the outset of a trial to determine how much Jones must pay for defaming them.

Jones created a “massive campaign of lies” and recruited “wild extremists from the fringes of the internet … who were as cruel as Mr Jones wanted them to be” to the families of the 20 first-graders and six educators who were killed in the 2012 attack on the school in Newtown, Connecticut, attorney Mark Bankston said during his opening statement as Jones looked on and occasionally shook his head.

Jones tapped into the explosive popularity of Sandy Hook conspiracy stories that became an “obsession” for the website, even years after the shooting, said Bankston, who played video clips of Jones claiming on his program that the shooting was a hoax and “the whole thing was completely fake”.

“It just didn’t happen,” Jones said in the clips.

Anticipating what Jones’s defense would be, Bankston told the jury, “This has nothing to do with the constitution. Defamation is not protected by freedom of speech … Speech is free, but lies you have to pay for.”

He said his clients, Neil Heslin and Scarlett Lewis, whose six-year-old son Jesse was killed in the attack, will ask for $150m for emotional distress and reputational damage, and more money in punitive damages.

During his opening address, Jones’s lawyer Andino Reynal called Jones one of the “most polarizing figures in this nation”, who made statements about Sandy Hook “that we don’t dispute were wrong”.

But he said Jones has already been punished for those statements when he was kicked off of Facebook, YouTube, Spotify and Twitter for violating their hate speech policies.

Jones has “already been cancelled” and lost millions of dollars, said Reynal, who called on the jury to limit the damages to $1.

Reynal painted a picture of a talkshow host who “tries to give an alternative view” but who was duped by some of his guests.

“Alex Jones was wrong to believe these people, but he didn’t do it out of spite,” Reynal argued. “He did it because he believed it … He believed a citizen has a right to get on Infowars and talk about what their questions are.”

He also called the case an important one for free speech.

“I believe in his right to say it, and I believe in every American’s right to choose what they watch, and listen to, and believe,” Reynal said.

Among those expected to testify on Tuesday are Daniel Jewiss, who was the Connecticut police lead investigator of Sandy Hook, and Daria Karpova, a producer at Infowars.

The jury could deal Jones a major financial blow that would put his constellation of conspiracy-peddling businesses into deeper jeopardy. He has already been banned from YouTube, Facebook and Spotify for violating their hate-speech policies and he claims he is millions of dollars in debt – a claim the plaintiffs reject.

Immediately after the plaintiffs’ lawyer’s opening remarks and before his own lawyer addressed the jury, Jones stepped outside the courtroom to rant to reporters, calling it a “kangaroo court” and “show trial” that was an assault on the first amendment of the constitution.

The Texas court and another in Connecticut found Jones liable for defamation for his portrayal of the Sandy Hook massacre as a hoax involving actors aimed at increasing gun control. In both states, the judges issued default judgments against Jones without trials because he failed to respond to court orders and turn over documents.

In total, the families of eight Sandy Hook victims and an FBI agent who responded to the school are suing Jones and his company, Free Speech Systems.

Jones has since acknowledged that the shooting took place. During a deposition in April, Jones insisted he was not responsible for the suffering that Sandy Hook parents say they have endured because of the hoax conspiracy, including death threats and harassment by Jones’s followers.

Jones claimed in court records last year that he had a negative net worth of $20m, but attorneys for Sandy Hook families have painted a different financial picture.

Court records show that Jones’s Infowars store, which sells nutritional supplements and survival gear, made more than $165m between 2015 and 2018. Jones has also urged listeners on his Infowars program to donate money.

The Texas trial begins about two months after a gunman killed 19 children and two teachers at Robb elementary school in Uvalde, about 145 miles south-west of Austin. It was the deadliest school shooting since Sandy Hook.