The case sparked outrage as it became a flashpoint over police violence and racial bias because Amber Guyger is white, while her victim was black.
Guyger, who worked in Dallas, claimed that she believed she had returned to her own apartment on September 6, 2018, and that she thought Botham Jean, 26, was an intruder.
In fact, the 31-year-old had entered Jean’s unlocked apartment, located in the same building but one floor above hers.
“We the jury unanimously find the defendant, Amber Guyger, guilty of murder as charged in the indictment,” the jury foreman announced.
After the verdict was read, Jean’s mother, Allison Jean, stood and looked upward as she celebrated the decision, raising her arms high and wide.
“I cannot sleep, I cannot eat, it’s just been the most terrible time for me,” she later told the jury that will decide on Guyger’s sentence.
“I try to busy myself to try to get this out of my head. It is very difficult.”
The jury, which retired on Monday, deliberated for five hours before delivering its guilty verdict.
Guyger, who was off duty after a nearly 14-hour shift, lived in apartment 1378 on the third floor, while Jean lived in apartment 1478 directly above her.
“She knows she’s made a tragic mistake, but it’s not out of evil,” Guyger’s lawyer, Robert Rogers, told the court when the trial opened, describing it as human error and an act of self-defence.
Guyger – a police officer for four years until her sacking following the shooting – sobbed when she took the stand last week.
“I ask God for forgiveness, and I hate myself every single day,” she said, voice trembling.
“I wish he was the one with the gun who had killed me. I never wanted to take an innocent person’s life.”
After hearing the verdict, Guyger stood as the jury filed out of the courtroom and then sank into her chair.
Prosecutor Jason Hermus said Jean, a native of the Caribbean island of St Lucia who worked for an accounting firm, “paid the ultimate price” for Guyger’s errors.
“She walks past 16 different apartments and fails to register the number four on any one of them,” Hermus said during the testimony phase of the trial last week.
Prosecutors played Guyger’s frantic 911 call, in which she repeatedly tells a dispatcher she is in the wrong apartment.
Bodycam footage from responding officers showed them trying to save his life as he lay bleeding, US media reported.
The shooting and its aftermath sparked demonstrations and appeals for justice in a nation where white police officers who shoot people of colour often go free.
Demonstrators rallied outside the Dallas police headquarters and city hall.
Jurors were given the option of finding Guyger guilty of the lesser offence of manslaughter, but a grand jury indicted her on the more serious charge of murder following the protests.
She faces up to life in prison when she is expected to be sentenced later on Tuesday. (AFP)