A man who murdered his girlfriend’s lover in a fit of rage after finding them in bed together has been sentenced to at least 12 years’ jail.

Roy Tabalbag wept in the dock on Monday as the Supreme Court heard he was like a “demon possessed” when he stabbed Amin Sthapit 14 times at his Darling Point unit in Sydney’s east on November 11, 2013.

Tabalbag always admitted he delivered the fatal wounds but pleaded guilty to manslaughter and not guilty to murder on the basis of provocation.

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This was rejected by a jury who convicted him of murder in June.

In sentencing him to a maximum of 17 years, Justice Michael Adams said Tabalbag was “filled with hatred and rage” when he pursued Mr Sthapit around the apartment with the knife.

“(Tabalbag said) had he been of right mind, he wouldn’t have done what he did. It seems to me this is the all too tragic truth,” Justice Adams found.

In the weeks before the attack, the court heard Tabalbag had become suspicious of his long-term girlfriend Gee Cy Rebacus and used software to read her deleted text messages.

On the morning of the murder, he used the Find My iPhone App on his mobile to locate hers and went back to the apartment.

Upon seeing her lying naked with Mr Sthapit he exclaimed: “Why, why did you do this?”

Grabbing her chef’s knife, he pursued Mr Sthapit who tried to take shelter in the bathroom.

Tabalbag ripped the door off its hinges before stabbing Mr Sthapit and following him around the bedroom.

When Ms Rebacus tried to halt the attack, he said: “Don’t try to stop me or I will stab you”.

He later handed himself into police.

Justice Adams said while it was plain the conduct of Mr Sthapit and Ms Rebacus “gave rise to his uncontrolled response” it “does not and cannot allow or excuse violent attacks that are not in self defence”.

“There is nothing about the conduct of Ms Rebacus or Mr Sthapit that could justify in any sense or to any degree the attack.”

But he said Tabalbag was a man of previous good character who had shown genuine remorse and was unlikely to reoffend.

He will be eligible for parole in November 2025.