Nothing like a three-hour deposition under oath to turn an excitable conspiracy theorist into a man subdued, deferential and humbled. That’s the Alex Jones who the world met for the first time on Friday, when attorneys for families of the victims of a school shooting posted his deposition online.

The deposition was given earlier this month in conjunction with a number of lawsuits on behalf of parents of victims of the attack in 2012 at Sandy Hook Elementary School in Newtown, Conn. Mr. Jones, the longtime misinformation-peddler and founder of the radio and online show Infowars, is being sued for defamation for saying repeatedly during his broadcasts that parts of the Sandy Hook shooting were staged and that the tragedy was a “false flag” operation, designed to take away firearms from American citizens.

For anyone familiar with his broadcasts and style, the deposition is a jarring piece of evidence. It is also perhaps the most revealing portrait of Mr. Jones — one that strips bare the bloviating host to expose a huckster. Amid his heavy sighing and wincing, the hours of out-of-court testimony show the real Alexander Jones: a man caught between the desire to defend his conspiracy empire and a legal system that threatens to bring it all crashing down.

On camera and in public, the stocky Texan is famous for his meandering soliloquies and belligerent, occasionally violent verbal outbursts. The Alex Jones persona orbits around his volatility, keeping audiences entertained and colleagues on their toes. It’s never quite clear whether he’ll laugh and burst into song, pound the table in a fit of rage or begin dramatically weeping.

The deposition video features Mr. Jones from the waist-up, sitting at a table — a camera angle similar to his online broadcasts. However, unlike an Infowars episode, the host is not in control. Instead, Mr. Jones is peppered with aggressive questions from an attorney. His confidential sources are exposed to be message board trolls and cranks. He’s made to read from a disturbing police report, chronicling the testimony of emergency medical workers who attended the shooting at Sandy Hook, and then immediately watch footage of his past broadcasts, in which he declares that elements of the violence were part of a “false flag” operation.

In the video, Mr. Jones occasionally attempts to slip into his Infowars persona. But his digressions are dismissed by lawyers as “nonresponsive.” At one point, Mr. Jones, evidently weary from questioning, asks for clarification of the lawyers’ meaning of the word “staged.” His question is cut off. “I’m not here to answer your questions,” the lawyer says. “You’re going to tell me what staged means when you said it.”

“This is such a rare public insight to his character and integrity,” Joshua Owens, a former Infowars employee who worked closely with Jones until 2017, told me on Friday evening after watching the deposition. “As someone who regularly saw his dynamic with others, no one speaks to him like this. [No one] asks these kinds of questions, pressures him to answer, or expects him to remain composed long enough for it to go anywhere productive.” Mr. Owens left Infowars after disagreements with Mr. Jones.

For more than two decades, Mr. Jones has built a big business on specious claims and fear-mongering. When pressed on false claims by critics, his classic response tends to be that he’s merely asking questions others are too afraid to ask.

Portions of the deposition are vintage Infowars: Mr. Jones blames “the media”; suggests that he is actually the person who is the victim of an unfair smear campaign; casts doubt on the veracity of the Infowars clips the lawyers have presented to him as evidence and suggests they’ve been heavily edited and that the audio was altered.

“That’s Alex Jones’s M.O.,” Owens said of the deposition. “To flood any topic with confusion and doubt so no one can grab onto anything.”

But under oath, Mr. Jones’s tactics fizzle. And the deposition highlights a troubling reality: The legal system may be the only way to defang a well-known conspiracy theorist at the height of his powers. Not only does the parade of lawsuits related to the Sandy Hook shooting cast him as a villain, but they threaten to expose and, perhaps drain, the funding sources that keep Infowars running without advertisers. There’s plenty at stake; documents reviewed by The New York Times last September suggest the bulk of Mr. Jones’s money comes from his business selling supplement products, allegedly netting more than $20 million in revenue per year.