The Tulsa, Oklahoma police officer who shot and killed motorist Terence Crutcher entered a plea of not guilty during a hearing on Friday.
Officer Betty Shelby was charged with 1st-degree manslaughter in her first court appearance following her arrest.
She turned herself in last week and is free on $50,000 bond.
Shelby's attorney, Scott Wood, claims Shelby was temporarily deaf by sirens during the September 16 shooting.
“She didn't hear the gunshot, didn't hear the sirens coming up behind her just prior to the shot,” Wood said Thursday.
Wood said his client's condition is called “auditory exclusion,” and it happens when people are in high stress situations.
Shelby reportedly tuned out the noise of arriving officers and she didn't hear the gunshot when she squeezed the trigger.
“It's not only a common phenomenon described in literature, but it's the No. 1 perceptual distortion by people I have represented who have been involved in shootings — diminished sound or complete auditory exclusion,” Wood said.
Wood didn't explain how diminished sound or deafness caused Shelby to shoot an unarmed man.
Shelby maintains she "feared for her life" when she opened fire. But another officer discharged his taser at Crutcher simultaneously when Shelby fired.
The arrest warrant stated Shelby "acted unreasonably by escalating the situation” when she shot and killed Crutcher.