The Hawke's Bay teenager who murdered Haumoana man Mark Geoffrey Beale in February last year has been sentenced to life imprisonment with a minimum non-parole period of 14 years.

Johnnie Puna, now aged 20, appeared before Justice Helen Cull QC in the High Court at Napier this morning.

He was found guilty of murdering 45-year-old Beale, who was found near the Tukituki River mouth with unsurvivable brain injuries on Waitangi Day last year, at the end of a four-day trial in November.

This morning Justice Cull QC began her sentencing by acknowledging Puna would receive a second strike for the offending after being convicted of aggravated robbery in 2016.

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This meant he was subject to a sentence of life imprisonment without parole unless it was manifestly unjust, and Justice Cull QC said she had determined it would be manifestly unjust.

She accepted Puna had been deeply affected by the offending, as shown in his remorse following Beale's death, and acknowledged his youth, cultural background and level of intoxication.

Puna had "positive prospects for rehabilitation" and acknowledged he wished to address his anger and alcohol issues, she said.

She imposed a minimum non-parole period of 14 years' imprisonment, stating it would more than adequately hold him to account for the harm he had caused.

Puna fatally attacked Beale just hours after meeting him in a chance encounter in the seaside settlement on the evening of February 5.

Beale, a father of two, lived an isolated life in the seaside settlement and loved to fish, often casting a net and chatting to others fishing on the beach.

He met Puna this way and, after sharing his home-brew vodka with him, returned to his home with the teenager for more alcohol when he accidentally fell down a bank and pulled Puna down with him.

At the trial it was heard Puna delivered 13 full-forced kicks to Beale's head, an assault that latest between 40 minutes and one hour, before urinating on him and leaving him for dead in the seaside settlement.

The 45-year-old's bloodied and beaten body was found by members of the public on the morning of Waitangi Day.

He had unsurvivable brain injuries and died just after midnight the following day after a ventilator supporting his breathing was switched off.

At sentencing this morning, Manning submitted the combination of brutality, cruelty of Puna and vulnerability of Beale warranted a minimum non-parole period of 17 years.

He described the attack as "senseless and gratuitous violence" and said it epitomised a complete lack of humanity towards the deceased.

On the subject of a minimum non-parole period of 17 years, Forster submitted there wasn't any murder that wasn't brutal or callous, and argued for a minimum non-parole period of 12 years instead.

He said his client's disadvantage, background and intoxication meant he had trouble regulating his behaviour, rather than having a sinister state of mind.

"This is a case where someone has lost control rather than a callousness to another human being's life."

Puna pleaded guilty to stealing the dead man's cellphone and vaping device.

Justice Cull QC sentenced him to one month imprisonment for each of the two theft charges to be served concurrently with his sentence for murder.

It was accepted at the outset of the trial that Puna delivered the blows that caused Beale's death.

However the intent, or recklessness, in which these blows were inflicted was the subject of the High Court trial.

Manning argued it was murder, by way of Puna either intending to kill Beale or intending to cause bodily injury he knew was likely to cause the man's death.

Forster said the teenager did not have murderous intent but was young and drunk, and did not realise the injuries could be fatal; submitting the appropriate verdict was manslaughter.

The jury deliberated for three hours before delivering a unanimous guilty verdict.