A white Oklahoma police officer who fatally shot an unarmed black man has been found not guilty of first-degree manslaughter.

Tulsa officer, Betty Shelby, killed 40-year-old Terence Crutcher on 16 September in a confrontation caught on video.

The jury reached its verdict after about nine hours of deliberations.

Dashcam and aerial footage of the shooting showed Mr. Crutcher walking away from Ms. Shelby with his arms in the air.

However, the footage did not show a clear view of the moment she fired the shot that killed him.

The policewoman said she fired because he did not obey her commands to lie on the ground and appeared to reach inside his SUV through a partially open window for what she thought was a gun.

Ms. Shelby also said she feared Mr. Crutcher was under the influence of PCP, a powerful hallucinogenic known as Angel Dust that makes users erratic and unpredictable.

An autopsy showed Mr. Crutcher did have PCP in his system, and police said they found a vial of it in his SUV. No weapon was found in the vehicle.

Mr. Crutcher’s killing was among a spate of shootings at the hands of police in recent years in the U.S., fueling the Black Lives Matter movement and prompting calls for more police accountability.

Prosecutors said there was no reason for Ms. Shelby to fire on a man who was walking away from her, and that she escalated a routine traffic matter into a deadly confrontation by acting unreasonably.

Her defence lawyer argued that prosecutors charged her for political reasons, looking to avoid protests and civil unrest.