A Mongrel Mob member facing more than six years in jail is appealing his manslaughter sentence on the grounds being Maori puts him at a social disadvantage.

The Court of Appeal reserved its decision, with a judge labelling the request as "radical" during the hearing in Auckland today.

Jessie Mika, who has been involved with a gang since he was 16 and has "Mobsta" tattooed across his face, was sentenced in September to six years and nine months in jail for causing the death of a teenage boy during a car chase in Canterbury.

TV3 'DISADVANTAGED': Fabian Jessie Mika is seeking a reduced sentence because he is Maori.

Christchurch defence lawyer James Rapley said Maori should receive shorter prison sentences because they come from an environment of social deprivation and inequality.

"Fifty-one per cent of the prison population is Maori," he told the Court of Appeal. "Everyone says everyone should be treated alike and equally, but not everyone is equal."

Mika was brought up by his aunt after his father walked out and his mother was unable to care for him, he said.

"Before he knew it, at the age of 14 or 15, he was associating with gangs," Rapley said.

He suggested a 10 per cent reduction in Mika's sentence due to his Maori heritage.

The three Court of Appeal judges said they struggled with the concept of reducing a sentence based on race.

"You're asking us to take a pretty radical step and we just won't do it on a wing and a prayer," Justice Rhys Harrison said.

"Because he has some Maori blood - and we're not sure how much - he's somehow less blameworthy or culpable. That's an extraordinary proposition."

Justice Robert Dobson said he agreed the prison ethnicity statistics were appalling, but making ethnicity a mitigating factor in sentencing would not solve the problem.

The judges also asked Rapley how such a rule would be interpreted, including whether a person who was 1/16th Maori would be given a lighter sentence.

A 15-year-old boy died when Mike crashed a stolen vehicle in Bromley on February 22.

A court was told that Ethan Takitimu-McKenzie, a passenger in the crashed car, was left lying in the grass to die of massive head and chest injuries.

He admitted the manslaughter charge, failing to stop for police, failing to ascertain injury after an accident and being an unlicensed driver.

In September, at his High Court sentencing Rapley also asked the court to take into account Mika's cultural background to reduce the sentence.

However, this was rejected by Justice David Gendall.

He said the personal circumstances of an offenders were always taken into account. "However, the law in this country is clear that no special discount for race, culture, or ethnicity matters alone is appropriate."

In his submissions to the Court of Appeal Rapley further argued that such considerations now applied in Canada, and had been applied in Australia until recently.

District Court Judge Stephen O'Driscoll had recently noted that Maori offenders made up a disproportionately large element within the prison population.

Maori make up 15 percent of the general population, but 51 percent of the prison population.

The Sentencing Act had reinforced the need to address the shocking statistic of disproportionate Maori imprisonment, Rapley said.

New Zealand had the second highest imprisonment rate in the world, with an overrepresentation and disproportionate rate of Maori prisoners. "This has attracted comment from the United Nations and overseas media."

Rapley urged the court to acknowledge and accept that the cultural background of Maori had been historically one of social deprivation and inequality and at present was disproportionately incarcerated.

"Everyone recognises there has been a history of colonialism, displacement, high unemployment, lower educational attainment and high level of incarceration for Maori," Rapley said.