Gordon Hieatt, 48, a self-employed computer programmer from Auckland, has pleaded not guilty in the High Court at Auckland to murdering his girlfriend Nuttidar Vaikaew, 48, a Thai sex worker.
His lawyer, Peter Kaye, said Ms Vaikaew had "developed a very harsh way of talking" and they started having increasingly heated arguments.
On the night of the killing, April 17 2009, the two got into a "fighting match" about rent money and she began shouting and abusing him.
Hieatt got some masking tape and placed it over her mouth but she ripped this off and a struggle ensued.
"The noise continued, the abuse continued, he couldn't shut her up."
He got a small rope from under the bed and began strangling her, "powerless to stop himself", Mr Kaye said.
"Something just snapped, it was like he was a spectator watching a movie. In what seemed like moments of time she was dead."
He straightened up her body, cleaned her, laid her on the bed and spent the night with her.
Any "horrible" suggestion that something sexual happened was vehemently denied, Mr Kaye said.
Ms Vaikaew immigrated to New Zealand from Thailand in 2001 and operated as a sex worker from the apartment.
She and Hieatt had been in an "on again off again" relationship for about two-and-a-half years.
Her body was found on May 12, 2009, nearly a month after he choked her to death.
Hieatt lived in the apartment for much of this time.
The provocation defence was abolished by the Government last year but could be available to Hieatt because the alleged offence took place before the law change.
It can reduce a conviction of murder to one of manslaughter.
