Kim Potter is charged with first and second degree manslaughter over the fatal shooting of Daunte Wright, 20, in Brooklyn Center in Minneapolis.
A US former police officer on trial for the death of a young African American man wept in court as she described how a routine traffic stop descended swiftly into chaos.
She claims the shooting was an accident, saying she mistakenly grabbed her gun instead of her Taser.
"We were struggling, we were trying to keep them from driving away. And then it just went chaotic, I remember yelling 'Taser Taser Taser.' And nothing happens, then he told me I shot him," Potter said on Friday, bursting into tears.
She testified that she was “sorry it happened" and she added the moments that followed were largely a blank.
"They have an ambulance for me and I don't know why. And then I went, then I was at the station. I don't remember a lot of things afterwards," she said.
On Sunday, April 11, 2021, the white policewoman was patrolling with a colleague who decided to look up the driver of a white Buick that had committed a minor traffic violation.
After realising that the driver was the subject of an arrest warrant, the police officers decided to arrest him.
'You don't know who you're stopping'
Potter described that as a potentially dangerous situation.
"Sometimes there's guns in the car. Sometimes there's uncooperative people, you don't know who you're stopping," she told the court.
Wright, who was unarmed, resisted being handcuffed and restarted his car to try to flee. Potter then drew what she said she thought was her Taser.
On a recording of the scene, Potter can be heard shouting "Taser" several times, before shooting with her gun and fatally wounding Wright.
The incident came during the trial of white policeman Derek Chauvin who had asphyxiated George Floyd in Minneapolis in May 2020 by kneeling on his neck for some nine minutes.
Floyd's death sparked nationwide protests against racism and police brutality.
Wright's death also triggered several nights of protests and unrest in Brooklyn Center before Potter's own arrest calmed tensions.
Potter's lawyer, Paul Engh, argued that Wright's death was a result of human error and the stress that his client was under, maintaining that she was attempting to protect a fellow officer as Wright tried to drive off.
But for prosecutor Erin Eldridge, Wright died because of Potter's reckless handling of her weapon and the negligence of an officer with 26 years on the force.