Convicted murderer Paul Mulvihill has denied lying during a sentencing hearing and says he has sought counselling for his infidelity issues.

Convicted murderer Paul Mulvihill says his actions caused the death of his former lover and ruined the lives of many others.

He says he shouldn’t have left Rachelle Yeo’s Sydney unit the way he did on July 16, 2012, and he shouldn’t have persisted with her once she called off their affair.

But Mulvihill has told the NSW Supreme Court he did not intend to kill the 31-year-old.

The 46-year-old provided evidence during a sentencing hearing on Friday.

Mulvihill was convicted of murdering Ms Yeo by stabbing her in the neck and chest after following her into her North Curl Curl unit in Sydney’s north.

“There is absolutely no excuse for leaving the way I did,” he said.

“I never intended to kill her but my actions did cause her death.”

Mulvihill has denied several violent occasions claimed by his first wife Celine Carroll, including that he waved a rifle around her and grabbed her around the throat.

He denied sending Ms Carroll a goodbye and good luck card with a bullet after their short marriage broke down in the 1990s.

“Definitely no bullet,” Mulvihill said.

“I did on a few occasions send cards and letters or leave cards or letters outside her unit.”

Mulvihill admitted he crept through a window in Ms Carroll’s Brisbane home after they broke up and hid under her bed because he wanted to “catch her out” with another man.

He told the court when Ms Carroll came home, he had a shoving match with the man she was with.

He denied he said: “I’m going to kill you”.

Mulvihill told the court he had sought counselling for his issues with infidelity and struggles to accept the end of relationships.

Through a quivering voice he he told the court he shouldn’t have gone to the Sydney unit of work colleague Ms Yeo on July 16, 2012.

“It’s the worst decision of my life and has ruined the lives of many,” he said.

Mulvihill said when he got into an argument and struggle with Ms Yeo and a knife was brought out, he should have left immediately.

Mulvihill’s trial heard the former rugby player jumped off Ms Yeo’s balcony and was arrested the following day at Brisbane Airport.

Crown prosecutor Maria Cinque suggested Mulvihill was lying like he did in his trial.

The hearing continues.