A man who stabbed his wife to death on the forecourt of a Wellington service station was today jailed for life, with a minimum non-parole period of 14-1/2 years.

Emani Tinoa'i, 49, a butcher, was sentenced in the High Court at Wellington after being found guilty of murdering Moliga Tinoa'i, 42, on the forecourt of a Johnsonville service station on March 14 last year.

Tinoa'i admitted the slaying at his trial but defence lawyer Mike Antunovic argued that he "lost his mind" after finding his wife had been unfaithful.

He stabbed her to death in a "frenzied explosion of passion".

Mr Antunovic said Tinoa'i was provoked by long-standing problems within his marriage, including his wife's infidelity.

"This was a killing by a human being in deep despair," he said.

Tinoa'i had long suspected his wife of cheating and had decided to give her "one last chance".

He went to her work and waited in her car with "five or six" beers and a knife.

Mr Antunovic said Tinoa'i wanted to talk to his wife and work through their problems but he "snapped" when she attempted to avoid the discussion by getting out of the car.

"Her getting out of the car triggered this frenzied explosion of passion," he said.

"The entire time that knife was in his hand he was out of control. He snapped. A seemingly minor act, he lost all control."

Mr Antunovic said Tinoa'i slashed wildly, striking his wife 18 times.

Tinoa'i's calm, dazed state after the attack was further evidence he had temporary lost his mind, he said.

Tinoa'i told the trial jury he began to suspect his wife was having an affair as early as 2007 and that their relationship was becoming more and more strained in the period leading up to the stabbing.

He said he thought his suspicions were confirmed when he saw what he thought was a "love bite" on his wife's chest the night before the attack.

Crown prosecutor Grant Burston said Tinoa'i had a history of violence toward his wife and repeatedly threatened to kill her.

"This killing was not a case of loss of self control, this was the final expression of Mr Tinoa'i's attempts to control his wife," he said. "He threatened to kill her and he did."