A federal jury in the US has convicted a former Kentucky police detective of using excessive force on Breonna Taylor during a botched 2020 drug raid, where she was shot and killed by police.

The 12-member jury returned the late-night verdict after clearing Brett Hankison earlier in the evening on a charge that he used excessive force on Ms Taylor's neighbours.

It's the first conviction of a Louisville police officer who was involved in the deadly raid.

In 2020, according to a report by the Louisville Metro Police Department, her former relationship with convicted drug dealer Jamarcus Glover was what led police to suspect her home was used in the drug trade, a claim that Glover denies.

Ms Taylor's boyfriend at the time, Kenneth Walker, said the pair were asleep when police raided the apartment.

Hankison, 48, argued throughout the trial that he was acting to protect his fellow officers, former Sergeant Jonathan Mattingly and former detective Myles Cosgrove, after Mr Walker fired on them when they broke down Ms Taylor's door with a battering ram.

In 2020, Kentucky Attorney-General Daniel Cameron said police knocked and announced themselves at the apartment, which he said was backed up by an independent witness.

This was at odds with the claim Mr Walker, a licensed gun owner, made in 2020, who said they did not make clear they were police before coming into the apartment (aka a "no-knock" warrant).

Verdict brings jury to tears

Some members of the jury were in tears as the verdict was read about 9:30pm on Friday, local time. 

They had earlier indicated to the judge in two separate messages that they were deadlocked on the charge of using excessive force on Ms Taylor but chose to continue deliberating. 

The six-man, six-woman jury deliberated for more than 20 hours over three days.

Hankison fired 10 shots into Ms Taylor's glass door and windows during the raid, but didn't hit anyone. 

Some shots flew into a next-door neighbour's adjoining apartment.

Taylor's death helped spark 2020 protests

The death of the 26-year-old Black woman, who was unarmed, was one of a trio of cases that sparked racial injustice protests across the US.

The others were George Floyd in Minneapolis and Ahmaud Arbery in Brunswick, Georgia.

A separate jury deadlocked on federal charges against Hankison last year, while in 2022, a jury acquitted Hankison on state charges of wanton endangerment. 

The conviction against Hankison carries a maximum sentence of life in prison.

This jury had sent a note on Thursday to US District Judge Rebecca Grady Jennings asking whether they needed to know if Ms Taylor was alive as Hankison fired his shots.

That was a point of contention during closing arguments, when Hankison's lawyer Don Malarcik told the jury that prosecutors must "prove beyond a reasonable doubt that Ms Taylor was alive" when Hankison fired.

After the jury sent the question, Judge Jennings urged them to keep deliberating.

Mr Walker shot and wounded one of the officers. Hankison testified that when Mr Walker fired, he moved away, rounded the corner of the apartment unit and fired into Ms Taylor's glass door and a window.

Meanwhile, officers at the door returned Mr Walker's fire, with one of Cosgrove's shots killing Ms Taylor.

She died within minutes and no drugs were found at the apartment.

Shooting lasted about 12 seconds

Hankison's lawyers argued during closing statements on Wednesday that he was acting properly "in a very tense, very chaotic environment" that lasted about 12 seconds. 

They emphasised that Hankison's shots didn't hit anyone.

Hankison was one of four officers charged by the US Department of Justice in 2022 with violating Ms Taylor's civil rights. 

Thus far, those charges have yielded just one conviction: a plea deal from a former officer who was not at the raid and became a cooperating witness in another case.

Mr Malarcik spoke at length during closing arguments about the role of Ms Taylor's boyfriend, who fired the shot that hit former Sergeant Mattingly at the door. 

He said Mr Walker never tried to come to the door or turn the lights on as police were knocking and instead armed himself and hid in the dark.

"Brett Hankison was 12 inches [30 centimetres] away from being shot by Kenneth Walker," Mr Malarcik said.

Prosecutors said Hankison acted recklessly, firing 10 shots into doors and a window where he couldn't see a target.

They said in closing arguments that Hankison "violated one of the most fundamental rules of deadly force: If they cannot see the person they're shooting at, they cannot pull the trigger".

Neither of the officers who shot Ms Taylor — former Sergeant Mattingly and former detective Cosgrove — were charged in Ms Taylor's death. 

Federal and state prosecutors have said those officers were justified in returning fire since Ms Taylor's boyfriend shot at them first.

AP/ ABC