Amber Guyger, a white ex-officer, accidentally walked into her neighbour’s home and shot him dead as he ate ice cream.

An earlier version of this article stated that Guyger faced a mandatory life sentence. That was incorrect. She faced up to life in prison.

A Dallas jury found former police officer Amber Guyger guilty on Tuesday 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 6, 2018, killing of Botham Jean, a 26-year-old black accountant, by Guyger, who was coming off a 13-1/2-hour shift, sparked street protests – particularly when prosecutors initially opted to bring the lesser charge of manslaughter against the white former officer.

Cheers could be heard in the Dallas County, Texas, court after the verdict was read.

Family members of Jean and others embraced shortly after Judge Tammy Kemp announced that Guyger was convicted of murder.

Someone yelled, “Thank you, Jesus” following the verdict.

Botham Jean’s family arrives on the first day of the trial against former Dallas police officer Amber Guyger [File: Jeremy Lock/Reuters]

Guyger, who was fired following the fatal shooting, sat alone at the defence table and wept after the verdict announced.

Guyger faces up to life in prison for the slaying. She took the rare step of testifying in her own defence during her trial, tearfully expressing regret for shooting 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.

Hermus also told the jury that Guyger missed blatant clues that she was not in her own apartment – including the smell of marijuana smoke – because she was distracted after a 16-minute phone conversation on her commute with her former police partner. Guyger testified that the call was related to work.

After the shooting, many said the incident represented another case of a white officer shooting an unarmed black man.

In her testimony, Guyger told jurors that the shooting “is not about hate; it’s about being scared.”

Neither prosecutors nor the defence focused on race during the trial.