A jury has found Waikato man Cory Jefferies guilty of the murder of his partner Kim Richmond.

The jury of five men and seven woman in the High Court At Hamilton decided he did have murderous intent when he attacked his partner of 26 years on their way home from a party at the Arohena Hall in South Waikato on July 31, 2016.

The Crown had earlier told the jury the case came down to murderous intent and Jefferies' state of mind at the time.

Crown prosecutor Ross Douch explained that intent stretched across the spectrum from a well thought out execution to an almost instantaneous killing where the offender knows death is likely but carries on with the act anyway.

"What you're looking at there is that you have a position where the killer reaches a state where the level of animosity or anger to the victim reaches the point where he wants to do them harm and acts upon it but in doing that he realises that level of harm can be fatal and does it anyway."

Kim Richmond, above. (Photo: NZ Police)

He also urged the jury to put aside any thoughts that what happened between Richmond and her neighbour was an affair.

Jefferies had always admitted killing Richmond but said it was unintentional.

Defence counsel Tom Sutcliffe said his actions in disposing her body in Lake Arapuni were that of a desperate man.

However, the post-mortem examination had not revealed any broken bones which he submitted show how little intent there was in trying to kill her.

"The evidence clearly shows that Kim's death … was a spontaneous, unscripted event. How else could it be explained?"

The jury spent six hours deliberating on Friday. They were sent out just after 10am today before returning with their verdicts at 10.30am.