He leaped to his feet, spewing a barrage of four-lettered expletives at the camera, spittle flying from his mouth as officers restrained him.
"Let them do their jobs and see what happens," one of the officers repeated.
The mantra appeared to work as Kerr's ranting petered out.
"In through your nose, out through your mouth," the officers said, as the defendant was forced back to his seat.
While he was soothed for several moments, the respite was brief.
"F... you. F... the pigs," he yelled.
When Kerr made a racist slur, Judge Peter Rollo muted the in-court audio and proceeded with sentencing as the soundless hostility continued to play out on screen.
On May 26 the sentenced prisoner was being escorted to his cell at the Otago Corrections Facility by three Corrections officers, when his rage exploded.
When they reached the cell, Kerr became verbally abusive and issued threats.
As he was ushered inside, he grabbed the victim's elbow and pulled him in, falling backwards on to a mattress.
Kerr spat in the man's right eye then lashed out with his feet.
The court heard he kicked the victim once in the shoulder and once in the head before he was pepper-sprayed.
The victim was so disoriented in the aftermath that he did not realise he had been attacked until he viewed CCTV footage of the episode.
An unrepentant Kerr told police the Corrections officer "deserved what he got".
Judge Rollo said a psychologist's report described a "difficult upbringing" and cast light on what was behind the defendant's violent outbursts.
Kerr, the court heard, was housed in the prison's high-dependency unit.
For May's violence, the judge added four months' imprisonment to the sentence he is serving at present.
