A Sunshine West man who stabbed his partner and killed her secret husband has been sentenced in the Supreme Court to 15 years jail.

Hung Anh Vu was found guilty of the manslaughter of Hung Viet Nguyen and recklessly causing serious injury to Laura Chan, following an incident on August 5, 2017.

The court heard that Vu and Ms Chan were in a relationship and had two teenage sons together, but Vu had spent several years away from them while in jail for drug trafficking in New South Wales.

During that time, Ms Chan started a relationship with Mr Nguyen and they married in 2015.

When Vu returned from NSW in August 2016 he moved back in with Ms Chan, but she maintained her relationship with Mr Nguyen in secret.

The court heard that on the day of the killing, Vu had the secret relationship confirmed to him by his mother and sons. He invited Mr Nguyen to his home to confront him and Ms Chan.

He hid a hunting knife under a cushion on a dining table chair before the pair arrived.

A friend of Vu spoke to him that afternoon and, sensing Vu was agitated, went to the house and was present in the room when Vu confronted Ms Chan and Mr Nguyen.

The friend gave evidence that Vu was shouting at Ms Chan and Mr Nguyen to admit to their relationship, and at one point stood up with the knife in his hand, prompting the friend to grab him from behind in a bear hug. A struggle ensued, during which both Mr Nguyen and Ms Chan were stabbed.

The evidence of the friend and Ms Chan gave contrasting views of how the stabbings occurred, however a jury and Judge Andrew Tinney were satisfied Vu had inflicted the wounds.

Mr Nguyen collapsed and could not be revived. An autopsy revealed the knife had penetrated his aorta and pierced his lung.

Ms Chan was taken to the Royal Melbourne Hospital with a wound to the chest and spent four days in the trauma ward.

Vu initially told police the pair had stabbed themselves out of shame over their relationship, before changing his story to claim the stabbings occurred accidentally.

Judge Tinney said the premeditated nature of the crime made it a particularly serious case.

“Your attacks upon the two victims did not happen out of the blue,” Judge Tinney said.

“They occurred in the context of the relationship they were having behind your back, your having found out about that relationship, and the powerful anger and resentment that arose due to that knowledge.

“The sentence I pass on you must be such as to bring it home clearly to others in the community who may be minded to act with extreme violence … that such behaviour will be met with strong punishment.”

Vu will be eligible for parole in 11 years.