The startling turn came after Rittenhouse, in a high-stakes gamble, took the stand and testified that he was under attack when he shot three men, two fatally, during a night of turbulent protests in Kenosha in the summer of 2020.
"I didn't do anything wrong. I defended myself," the 18-year-old said.
During cross-examination, prosecutor Thomas Binger asked Rittenhouse about whether it was appropriate to use deadly force to protect property. The prosecutor also posed questions about Rittenhouse's silence after his arrest.
At that, the jury was ushered out of the room, and Circuit Judge Bruce Schroeder loudly and angrily accused Binger of pursuing an improper line of questioning and trying to introduce testimony that the judge earlier said he was inclined to prohibit.
Rittenhouse lawyer Corey Chirafasi all but suggested prosecutors might be deliberately trying to cause a mistrial because this one is "going badly" for the prosecution and it wants a do-over. The defense asked for a mistrial with prejudice, meaning that if one is granted, Rittenhouse cannot be retried in the shootings.
When Binger said he had been acting in good faith, the judge replied: "I don't believe that."
Rittenhouse is on trial for the shootings he committed during sometimes-violent protests that erupted in Kenosha over the wounding of a Black man by a white Kenosha police officer. He could get life in prison if convicted of the most serious charges against him.
Rittenhouse, who was 17 at the time, went to Kenosha with an AR-style semi-automatic weapon and a medic bag in what the former police youth cadet said was an attempt to protect property after rioters had set fires and ransacked businesses on previous nights.
Rittenhouse testified that he fatally shot Joseph Rosenbaum after Rosenbaum chased him and put his hand on the barrel of Rittenhouse's rifle. He said he then shot and killed Anthony Huber after Huber struck him in the neck with his skateboard and grabbed his gun.
When a third man, Gaige Grosskreutz, "lunges at me with his pistol pointed directly at my head," Rittenhouse shot him, too, wounding him.
"I didn't intend to kill them. I intended to stop the people who were attacking me," Rittenhouse said.
During his turn as a witness, Rittenhouse sobbed so hard at one point that the judge declared a break. But otherwise, he was composed on the stand, even as he was being cross-examined aggressively.
The case against Rittenhouse has divided Americans over whether he was a patriot taking a stand against lawlessness or a vigilante. Prosecutors have portrayed him as the instigator that night, while the defense has said he feared for his life, afraid that his gun was going to be taken away and used against him.
Rittenhouse's decision to testify carried certain risk - including the possibility of fierce cross-examination from prosecutors - and came despite doubts among some legal experts about the value of putting him on the stand, given the apparent weaknesses in the state's case.
During the prosecution's side of the case, some of its own witnesses bolstered the young man's claim of self-defense.
As he began crying on the stand and appeared unable to speak, his mother, Wendy Rittenhouse, on a bench across the courtroom, sobbed loudly. Someone next to her put an arm around her. After the judge called a recess, jurors walked by Rittenhouse and looked on as he continued to cry.
Much of the testimony Wednesday was centered on the first shooting of the night, since it was Rosenbaum's death that set in motion that bloodshed that followed.
Rittenhouse said he was walking toward a car dealer's lot with a fire extinguisher to put out a blaze when he heard somebody scream, "Burn in hell!" He said he responded by saying, "Friendly, friendly, friendly!"
He said Rosenbaum was running at him from one side and another protester with a gun was in front of him, "and I was cornered." He said that was when he began to run. He said another protester, Joshua Ziminski, told Rosenbaum, "Get him and kill him."
Rittenhouse said he heard a gunshot directly behind him, and as he turned around, Rosenbaum was coming at him with his arms out in front. "I remember his hand on the barrel of my gun," Rittenhouse said.
"I shoot him," the defendant recounted. He also said he thought the object Rosenbaum threw during the chase - a plastic hospital bag - was a chain he had seen Rosenbaum carrying earlier.
Rittenhouse said he intended to help the wounded man but was in shock as someone else attended to him. Rittenhouse said he thought the "safest option" was to turn himself in to police who were nearby.
Asked by his lawyer why he didn't keep running away from Rosenbaum, Rittenhouse said: "There was no space for me to continue to run to."
Rittenhouse said that earlier that night, Rosenbaum was holding a chain and had twice threatened to kill him. Apologizing to the court for his language, Rittenhouse quoted Rosenbaum as saying: "I'm going to cut your (expletive) hearts out!"
As he first took the stand, Rittenhouse was asked by his attorney whether he came to Kenosha looking for trouble, and he responded no.
He testified that he saw videos of violence in downtown Kenosha on the day before the shootings, including a brick being thrown at a police officer's head and cars burning in a Car Source dealership lot. Rittenhouse said the Car Source owner "was happy we were there" that night.
This story has been corrected to show that it was the defense attorney, not the judge, who suggested the prosecutor was trying to cause a mistrial.
Bauer reported from Madison, Wisconsin; Foody from Chicago. Associated Press writer Tammy Webber contributed from Fenton, Michigan.