David DePape lived a solitary life, worked carpentry jobs and was seemingly obsessed with right-wing conspiracy theories on the internet, where he railed about “wokism,” questioned the Holocaust and embraced Pizzagate and QAnon.
Then in October 2022, the police said, Mr. DePape, 43, busted into Nancy Pelosi’s San Francisco home and bludgeoned her husband, when she was still the House speaker. The authorities said he told investigators that he intended to take hostage Ms. Pelosi, long a subject of virulent attacks by right-wing leaders and pundits who have called her an enemy of the United States.
The case was presented to a jury on Thursday as Mr. DePape’s federal trial in San Francisco began, and his own defense lawyer said in her opening statement that Mr. DePape would not contest the evidence against him.
“This is not a whodunit,” Jodi Linker, a federal public defender, told the jury on Thursday morning.
Instead, Ms. Linker laid out a defense on narrow legal grounds: that Mr. DePape did not commit a federal offense because he was not driven by Ms. Pelosi’s official duties as a member of Congress but by a desire to stop what he thought was a larger political conspiracy.
Mr. DePape has been charged with two federal crimes: assault on an immediate family member of a federal official and attempted kidnapping of a federal official. If convicted, he could face life in prison. Even if Ms. Linker’s defense prevails, Mr. DePape faces several felony charges in state court that do not rely on Ms. Pelosi being a federal official.
Ms. Linker told jurors that Mr. DePape believed prominent liberal figures, including Hunter Biden, the president’s son; the actor Tom Hanks; and the billionaire George Soros, were involved in pedophilia, corruption and destroying American liberty.
She told jurors that much of what they would hear during the trial would sound “bizarre,” but that Mr. DePape believed the conspiracies with “every ounce of his being.”
The trial, expected to last a week, already has begun to spotlight the online disinformation cycle that has been fed by conspiracy theorists, conservative activists, elected officials and media outlets. Ms. Linker suggested — but did not say so directly — that Mr. DePape had fallen prey to the disinformation ecosystem, noting his consumption of podcasts and YouTube videos.
That the case came to trial at all was something of a surprise, given the evidence. The vicious assault on Paul Pelosi, who was 82 at the time, was captured on police body cameras. Mr. DePape admitted to the crimes in a police interview after his arrest, prosecutors say. He also called a local television station in January, saying that he acted to oppose tyranny and apologizing that he “didn’t get more of them.”
“I think he wants a trial,” said Laurie L. Levenson, a former federal prosecutor who teaches at Loyola Law School in Los Angeles. “He wants to use this as his platform, as a showcase for his beliefs. I think the court will shut it down, but it’s the same reason he called the media from prison to talk about the case.”
Laura Vartain, the trial prosecutor, began her opening argument by holding up the large hammer that Mr. DePape had used to bash Mr. Pelosi’s head. “He had a plan — it was a violent plan,” Ms. Vartain said. “He planned to hold her hostage, to break her kneecaps, to teach her a lesson.”
At the time of the attack, in the early morning hours of Oct. 28, 2022, Ms. Pelosi was in Washington and her husband was asleep in the couple’s home in the upscale Pacific Heights neighborhood of San Francisco.
“Where’s Nancy?” the intruder asked repeatedly. When Mr. Pelosi asked why he wanted to see her, the man responded, “Well, she’s No. 2 in line for the presidency, right?” according to the authorities.
When the police arrived shortly after Mr. Pelosi surreptitiously called 911, officers found Mr. Pelosi and the intruder standing calmly, each with a hand on a hammer. After the police asked them to drop it, the intruder seized the weapon and slammed it into Mr. Pelosi’s head.
In court on Thursday, the prosecution showed the jury a photograph of Mr. Pelosi, head down as blood spread across the floor. He suffered a skull fracture that required surgery and spent six days in a San Francisco hospital.
The attack raised fears of political violence in the run-up to last year’s midterm elections, and many saw it as a consequence of years of right-wing attacks against Ms. Pelosi, often with dehumanizing language.
In an interview with San Francisco police after his arrest, Mr. DePape said he intended to hold Ms. Pelosi hostage and interrogate her, according to the federal complaint. Mr. DePape “articulated he viewed Nancy as the ‘leader of the pack’ of lies told by the Democratic Party,” according to the complaint, and said he was going to break “her kneecaps” if she lied to him.
The police seized a long list of items they say Mr. DePape was carrying when they arrested him, including zip ties, duct tape, a passport, two driver’s licenses and $9,126 in cash.
After opening statements, the prosecution called six witnesses, all police officers who either responded to the scene, processed the evidence or interviewed Mr. DePape after his arrest while he was handcuffed to a bed at a hospital.
At the conclusion of the interview, portions of which were played in court, Lt. Carla Hurley asked Mr. DePape if he was taking any medication, because, she said, what he had told her was, “so jarring and disturbing.”
“No,” Mr. DePape responded. “I knew exactly what I was doing. I am not of unwell mind.”
Mr. Pelosi is expected to take the witness stand next week, possibly when the trial resumes on Monday.
While much of the evidence against Mr. DePape has been in the public sphere for months, one mystery had been hanging over the trial as it began: the identity of “Target 1,” a person whom Mr. DePape has identified to the police as someone he was hoping to lure by taking Ms. Pelosi hostage. Despite objections from the prosecution, Judge Jacqueline Scott Corley has ruled that the defense can call “Target 1” as a witness.
In court on Thursday, “Target 1” was identified as a feminist scholar who teaches at the University of Michigan. Ms. Finker told jurors that Mr. DePape’s real objective was to use Ms. Pelosi to get to “Target 1.”
Mr. DePape, who is Canadian and was in the United States illegally when he was arrested, had lived for a time under a tree in a park in Berkeley, Calif., after leaving the home he shared for years with a former romantic partner. He had moved to the Bay Area in his 20s, dabbled in psychedelics, protested the Iraq War and sold hemp bracelets. Later, he worked in carpentry.
Interviews with people who knew Mr. DePape, as well as an examination of his voluminous online writings, painted a portrait of a man deeply absorbed by some of the most virulent right-wing conspiracy theories. According to his blog posts, the online harassment campaign Gamergate — which began in 2014 and had misogynistic undertones — was an entry point for him into the dark corners of the internet where homophobic and bigoted views flourish.
“We’re at a point now where you can’t actually ignore what’s happening on the dark fringes of the internet,” said Amarnath Amarasingam, a professor at the School of Religion at Queen’s University in Ontario and an expert on extremism. “Because more and more, they are having a spillover effect into real life.”
The attack spawned even more disinformation. Elon Musk promoted a conspiracy that involved male prostitution. Donald J. Trump thought the attack might have been staged. Tucker Carlson raised doubts about the facts, saying he was just “asking questions.”
The next hearing in the state case is scheduled for Nov. 29, when a judge is expected to set a trial date. By then, the federal trial will likely have concluded. If Mr. DePape is convicted and receives a lengthy prison sentence, state prosecutors could try to resolve their case with a plea deal or drop it entirely.