Jurors failed to reach a unanimous verdict on federal civil rights charges Thursday in the trial of a former Louisville police officer charged in the police raid that killed Breonna Taylor, prompting the judge to declare a mistrial.

Brett Hankison was charged with using excessive force that violated the rights of Taylor, her boyfriend and her next-door neighbors. Hankison fired 10 shots into the Black woman's window and a glass door after officers came under fire during a flawed drug warrant search on March 13, 2020. Some of his shots flew into a neighboring apartment, but none of them struck anyone.

The 12-member, mostly white jury struggled fruitlessly to reach a verdict over several days. On Thursday afternoon, they sent a note to the judge saying they were at an impasse. U.S. District Judge Rebecca Grady Jennings urged them to keep trying, and they returned to deliberations.

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The judge reported there were "elevated voices" coming from the jury room at times during deliberations, and court security officials had to visit the room. Jurors then told the judge Thursday they were deadlocked on both counts against Hankison, and could not come to a decision — prompting Jennings' declaration of a mistrial.

The mistrial could result in a retrial of Hankison, but that would be determined by federal prosecutors at a later date.

Federal prosecutors didn't immediately respond to an email afterward seeking comment.

Before the mistrial was declared, the lead federal prosecutor, Michael Songer, said in court that it would take "enormous resources … to retry this case." Songer wanted the jury to keep deliberating.

Jennings said she believed the jury would not be able to reach a verdict. "I think the totality of the circumstances may be beyond repair in this case," the judge said. "They have a disagreement that they cannot get past."

Lonita Baker, an attorney for Taylor's family, said afterward that Taylor's mother, Tamika Palmer, was disappointed with the outcome but remained encouraged "because a mistrial is not an acquittal. And so we live another day to fight for justice for Breonna."

Hankison, 47, was acquitted by a Kentucky jury last year on wanton endangerment charges. State prosecutors had alleged he illegally put Taylor’s neighbors in danger. Months after his acquittal last year, the U.S. Department of Justice brought the new charges against Hankison, along with separate charges against a group of other officers involved in crafting the warrant.

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U.S. Attorney General Merrick Garland said Taylor, a 26-year-old nursing student, "should be alive today" when he announced the federal charges in August 2022. The charges that Hankison faced carried a maximum sentence of life in prison.

Hankison was the only officer who fired his weapon the night of the Taylor raid to be criminally charged. Prosecutors determined that two other officers were justified in returning fire after one was shot in the leg.

Songer said Monday in the trial’s closing arguments that Hankison "was a law enforcement officer, but he was not above the law." Songer argued that Hankison couldn’t see a target and knew firing blindly into the building was wrong.

Hankison’s attorney, Stewart Mathews, countered that he was acting quickly to help his fellow officers, who he believed were being "executed" by a gunman shooting from inside Taylor’s apartment. Taylor’s boyfriend had fired a single shot when police burst through the door. Her boyfriend, Kenneth Walker, said he believed an intruder was barging in.

"If his perception was reasonable in the chaos of that moment, that was not criminal," Mathews said.

The night of the raid, Hankison said he saw the shot from Taylor’s boyfriend in the hallway after her door was breached. He backed up and ran around the corner of the building, firing shots into the side of the apartment.

"I had to react," he testified. "I had no choice."

The single shot from Taylor’s boyfriend hit former police Sgt. Jonathan Mattingly, who dropped to the ground and fired six shots. Another officer, Myles Cosgrove, fired 16 rounds down the hallway, including the bullet that killed Taylor. Mattingly testified as a defense witness for Hankison in the federal trial, while Cosgrove was called to testify by prosecutors.

Cosgrove was fired by Louisville police along with Hankison. Mattingly retired.

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Taylor’s death didn’t initially garner much attention, but after the death of George Floyd by Minneapolis police in May 2020 and the release of Taylor’s boyfriend’s 911 call, street protests over police brutality erupted around the country. Demonstrators in Louisville shouted Taylor’s name for months, along with high-profile Black celebrities like Oprah and Lebron James who demanded accountability for the police officers involved in the case.

Taylor's case also cast intense scrutiny on so-called "no-knock" warrants, which were later banned in the city of Louisville. The warrants allow officers to enter a residence without warning, but in the Taylor raid officers said they knocked and announced their presence. The Louisville police chief at the time was subsequently fired because officers had not used body cameras the night of the raid.

Three other former officers involved in drawing up the warrant have been charged in a separate federal case. One of them, Kelly Goodlett, has pleaded guilty to helping falsify the warrant. She is expected to testify against former detective Joshua Jaynes and former Sgt. Kyle Meany in their trial next year.

Goodlett’s guilty plea remains the only criminal conviction of a police officer involved in the Taylor case.