Brett Hankison was charged with using excessive force that violated the rights of Taylor, her boyfriend and her next-door neighbours.

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 neighbouring 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. US District Judge Rebecca Grady Jennings urged them to keep trying, and they returned to deliberations.

The judge reported there were "elevated voices" coming from the jury room at times 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.

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. Months later, the Department of Justice brought the new charges against Hankison, along with separate charges against other officers involved.

Attorney General Merrick Garland said Taylor "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.

The prosecution argued Hankison couldn't see a target and knew firing blindly into the building was wrong.

Hankison's lawyer, 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.

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 Walker's 911 call, street protests over police brutality erupted around the country, with demonstrators shouting her name.

The case also cast intense scrutiny on so-called "no-knock" warrants, which were later banned in the city of Louisville.

Australian Associated Press