King came before the Dunedin District Court this week after pleading guilty to threatening to kill.
On August 17, prisoners were being served their evening meal. A Corrections officer passed King's meal through the small hatch in his cell door and immediately found himself on the end of a tirade.
The inmate began abusing two of the staff members who were dishing out the food and ''when he saw the victim his demeanour escalated to rage''.
''In a very angry voice he looked directly at the victim and threatened to kill him,'' a police summary of facts said.
Judge Kevin Phillips said the threat featured obscenities.
When spoken to about the incident, King said he hated the victim ''with a passion'' and claimed a change in medication was behind his aggressive demeanour. He nonetheless called his comments ''banter''.
The court heard the Corrections officer had worked at the prison for six years and it was his first experience of such a threat.
He took it seriously and the incident had greatly upset his wife, the judge said.
King was sentenced to six months' imprisonment.
The term would not affect his parole-eligibility date but would be taken into account by the Parole Board when considering his suitability for release.