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A man who beat his pregnant partner to death in a Rotorua school ground has failed in an appeal bid after claiming magic mushroom use would 'prove he did not realise death was likely”.

Jayson Wiremu Poihipi​ has sought to appeal his murder conviction after his lawyer told the Court of Appeal his trial lawyer 'failed to prepare, investigate and advance key elements of the defence case”.

Poihipi was sentenced to life imprisonment with a minimum non-parole period of 10-years six-months in November 2019 at the High Court in Rotorua for what was described as a "sustained and frenetic attack".

As they walked through the grounds of Rotorua's St Michael's Catholic School the then 19-year-old Poihipi punched and kicked his 22-year-old partner Lynace Parakuka​ in the head between 11 to 20 times.

She was seven weeks pregnant.

The power behind the blows was enough to shift her brain, damage blood vessels in and around her brain and fracture her left eye socket. Poihipi watched Parakuka die for 20 minutes before calling for help.

The court had heard how Poihipi called for his cousin for help when he became concerned about Parakuka. They attempted to resuscitate her before an ambulance arrived, but were unsuccessful.

Initially Poihipi lied about the attack, claiming it was someone else who bashed her, but came clean the next day.

Citing 'trial counsel error” the appeal claimed there were failings to investigate and advance the issue of drug use, Poihipi's 'history of anger” and whether earlier injuries contributed towards Parakuka's death.

Jayson Wiremu Poihipi was jailed for life for the murder of his partner, Lynace Parakuka, who he killed in a school ground assault in 2018. Photo: Matt Shand/Stuff.

'Mr Poihipi says now that he was under the influence of psychedelic mushrooms and has used methamphetamine a few days prior,” the ruling said.

'He says that he wanted the mushroom use and proximate methamphetamine use to be put into evidence to prove that he did not realise death was likely.”

Poihipi's appeal lawyer Craig Tuck told the Court of Appeal 'there has been a miscarriage of justice”.

However, the Court of Appeal said there had been no evidence to suggest Poihipi was under the influence of magic mushrooms at the time, and 'only inconsistent evidence that he has consumed any”.

'The fundamental evidence confirming consumption and some effect had to be established before further evidence would be useful, and on the evidence available, it could not be,” the ruling said.

The ruling also said that even if a jury has accepted Poihipi was having drug-induced delusions, 'they would have had to believe that he did not appreciate his assault would be likely to cause death”.

'We note that diminished responsibility is not a defence, or partial defence, to murder in New Zealand,” the ruling said.

'We are satisfied there was no trial counsel error relating to a failure to investigate, prepare and advance key elements of the defence case.

'The appeal is dismissed.”

-Benn Bathgate/Stuff.