A former Dallas police officer who said she fatally shot her unarmed neighbour after mistaking his apartment for her own has been found guilty of murder.

A Dallas jury has found former police officer Amber Guyger guilty of murder when she accidentally walked into a neighbour’s apartment thinking it was her own and shot him dead as he ate ice cream.

The September 2018 killing of Botham Jean, a 26-year-old black accountant, by a white officer sparked street protests, particularly when prosecutors initially opted to bring the lesser charge of manslaughter against Guyger, 31.

“We the jury unanimously find the defendant Amber Guyger guilty of murder as charged in the indictment,” Judge Tammy Kemp read aloud to the courtroom from the jurors’ statement on Tuesday.

A sob, which sounded like it came from Guyger’s bench, cut the judge off and Kemp paused to address the courtroom.

“No outbursts,” she said.

Guyger, who spent four years on the force before the killing, faces a mandatory sentence of life in prison for the slaying.

“We, the jury, unanimously find the defendant, #AmberGuyger guilty of murder” pic.twitter.com/tJQAc4QamO

— philip lewis (@Phil_Lewis_) October 1, 2019

She took the rare step of testifying in her own defence during her trial, tearfully expressing regret for shooting Mr Jean but saying she had believed her life was in danger when she pulled the trigger.

“I’m so sorry, I’m so sorry. I have to live with this every single day,” Guyger told the jury of eight women and four men.

In cross-examination, Assistant District Attorney Jason Hermus asked her: “When you shot him twice, you intended to kill him, didn’t you?”

“I did,” Guyger responded, in a calm voice.

Prosecutors also argued that Guyger did little to help Jean even after realising her mistake, calling the 911 emergency phone number for an ambulance but not administering first aid.

– AAP