NSW one-punch law survives challenge

The one-punch killer of a young Sydney nurse outside a house party has failed to avoid an eight-year minimum jail term.

Hugh Bacalla Garth - the first person charged with the NSW offence introduced after the deaths of Sydney teenagers Daniel Christie and Thomas Kelly - had challenged its validity.

Garth argued the mandatory minimum sentence of eight years was constitutionally invalid because it was a case of the parliament restricting the judiciary.

He also argued it would be unjust for offenders who the justice system thought should receive lesser sentences actually copped jail terms identical to those for whom eight years was deemed appropriate.

Garth was found guilty earlier this year of assault causing death while intoxicated after he punched a stranger, Raynor Manalad, outside a party in 2014.

Prosecutors, at times supported by the NSW Solicitor-General Michael Sexton, argued the mandatory minimum was a constraint, not a distortion, on the court's ability to impose sentences.

District Court Judge Antony Townsend on Friday agreed. He was satisfied the mandatory minimum term acted as a sentencing yardstick.

Garth, who was in court to hear the decision, will be sentenced on December 8. He faces up to 25 years in prison.