Paul Darren Mulvihill held his head in his hands as a jury found him guilty of the stabbing murder of Rachelle Yeo on Sydney’s northern beaches.

After being convicted of stabbing his ex-lover Rachelle Yeo to death, Paul Mulvihill put his head in his hands and said “no” over and over.

At the back of the court, one of Ms Yeo’s supporters exclaimed “yes” before embracing other supporters in tears.

A jury needed just two hours on Monday to find Mulvihill, 46, guilty of murdering the 31-year-old in her North Curl Curl unit in Sydney’s north in July 2012.

The two had started an affair a year earlier when they worked together at Sanofi Aventis pharmaceuticals in Brisbane, while Ms Yeo was engaged and Mulvihill was married to his wife of 16 years.

Their romance began to unravel and, in April 2012, Ms Yeo accepted a promotion and moved to Sydney.

She hid her new address from Mulvihill, but he discovered it when he found a letter to her.

On July 16, 2012, he waited for her outside her apartment block and followed her upstairs and into her unit without her knowing.

Ms Yeo was found fatally stabbed in the neck and chest.

The court heard Mulvihill later called his wife and said “she’s gone”.

Wearing a yellow scarf signifying her murdered daughter’s energy, Kathy Yeo cried after Mulvihill was found guilty.

“It is extremely sad that we have lost our daughter but I am glad that (the jurors) were able to come with this verdict,” she said outside the NSW Supreme Court.

Ms Yeo’s father, Roger Yeo, said justice had been served but there were no winners.

“Unfortunately over 70 women are killed every year by the partner or ex partner and our daughter is one of them,” he said.

“It’s unfortunate that in cases like this a lot of evidence doesn’t come to light.

“Things like tendency and character and history don’t play a part because they give rise to a possibility of appeal.”

Mulvihill claimed he did not murder Ms Yeo and acted in self-defence when she lunged at him with a massive knife.

A neighbour told the court she heard a female voice inside Ms Yeo’s unit “begging for help and crying, very distressed”.

The case will return to court on March 28 for sentencing submissions.

Mulvihill’s lawyer asked for her client to be put on suicide watch.

* Readers seeking support and information about suicide prevention can contact Lifeline on 13 11 14 (plus one of the following depending on context)