The family of a man seriously assaulted in Auckland in 2015, who died several weeks ago, say it is unfair the man who hit him cannot be charged over his death.

No one can be held criminally responsible if a death occurs more than a year and a day on from the offence.

George Siaosi, 37, was punched by Pelepesite Poai after a late-night argument in a Manukau street in September 2015.

The youth worker fell down some stairs, and hit his head violently on concrete at the bottom.

Poai was sentenced to a year's home detention* and 300 hours' community work and ordered to pay reparation for wounding with intent.

Emergency surgery saved Mr Siaosi's life after the attack and fall, but he suffered a brain injury and later a stroke. He spent the next 15 months in rehabilitation and died on 4 January.

His victim's mother, Sandra Gray, told Checkpoint with John Campbell she wanted a law change.

"That was the first thing I thought of, after George's burial. What happens now? Does he go back to court, under a different charge? I was told 'no'. That's a total insult to my son."

Her son had fought hard to recover, she said.

"He more than survived, he struggled. He fought, all the time, to stay with us. He fought for himself, his friends, his family, everyone. But his body just wore out."

Justice Minister Amy Adams said this issue had not been raised with her before, and she has asked officials to look into it.

"I think it is worth reviewing the way Section 162 of the Crimes Act works. I've asked my justice officials for advice, and they will report back to me in due course."

* Clarification: The interview above made mention of the maximum sentence for wounding with intent as a year of home detention. It is in fact a maximum sentence of 14 years' imprisonment.