Former Gwinnett County police officer Robert McDonald testified Tuesday he did not intend to stomp on motorist Demetrius Hollins.

He also said he could not tell that Hollins was handcuffed at the time. All he knew was his sergeant, Michael Bongiovanni, was in a fight.

“I don’t know what’s going on,” said McDonald, now 28.

It’s been nearly three years since McDonald and Bongiovanni, both white, were caught on tape forcibly arresting Hollins, who is African-American. The officers were subsequently fired and criminally charged. Bongiovanni reached a plea deal last summer, agreeing to testify in McDonald’s trial in order to avoid prison.

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That threat still hangs over McDonald, charged with aggravated assault, battery and violation of oath of office. If convicted on all counts, he faces up to 26 years behind bars. Closing arguments are set for Wednesday morning.

The events of April 12, 2017, were captured in cellphone video that has been viewed more than 1 million times online.

McDonald, the only witness called by the defense, was confident and succinct in defending his actions that day. But that testimony seemed to contradict the video, deftly utilized by lead prosecutor Charissa Henrich in her cross-examination.

“You didn’t know or you assessed facts?” Henrich asked.

McDonald testified he was on the scene at a home burglary when he heard Bongiovanni, his supervisor, call for backup at the intersection of Lawrenceville-Suwanee Road and Sugarloaf Parkway.

The senior officer was typically “calm, cool and collected” on the police radio, McDonald said. But not this time.

“I heard that and thought, ‘Oh man, something’s really going on,’” he said.

When he arrived on the scene, Bongiovanni was standing over Hollins, having just used his Taser.

So what motivated McDonald to respond so aggressively, pinning Hollins to the pavement, his gun pointed at the suspect’s head?

"I was kneeling on the guy to keep him from rolling,” McDonald testified. A suspect on his side still posed a threat, he said.

Aiming his firearm at Hollins’ temple was necessary, McDonald explained, to protect others in the immediate vicinity.

"If, God forbid, you do have to take a shot, the bullet's going straight — it's not going to hit my sergeant or an innocent motorist,” he said.

On video, however, Hollins doesn’t appear to pose a threat to anyone, least of all two armed officers.

Hollins is seen on the pavement, prone and handcuffed, looking in McDonald’s direction.

“You see someone turning to you and your training tells you to kick him in the head?” Henrich asked.