A methamphetamine dealer who turned to crime to support his siblings as a teenager, after his father abandoned them, has had 19 months taken off his lengthy jail term.

Salesio Pomale was sentenced to 11 years in jail in 2019, when he was 26, on one charge of supplying methamphetamine, one of offering to supply it, and three charges of conspiracy to supply the drug.

Supplying or offering to supply methamphetamine has a maximum life sentence.

The High Court at Auckland was told in 2019 that Pomale's life "went off the rails" at the age of 12, when his father left home to work in Australia. Later, the father stopped sending money home.

The teenaged Pomale soon became involved with gangs and crime, feeling his father had abandoned his family and that he had a responsibility to provide for them.

Pomale was arrested in 2018 following a police investigation into a methamphetamine supply chain. He was described as the "middle man" between the main supplier, Richie To'a, and street-level salesman James Puhara.

In regard to the supply charge, Pomale passed on at least 721 grams of methamphetamine to Puhara and received $117,370 in return in 2017. In total, Pomale supplied or conspired to supply about 2.1kg of meth.

Although Pomale himself was addicted to methamphetamine, this did not drive his offending. He was considered a "major commercial dealer", according to court documents.

The sentencing judge, Justice Geoffrey Venning, made reference to a cultural report, for which the report writer spoke to members of Pomale's family, including two sisters, about his Tongan heritage and early development which was described as "positive and supportive".

But it said that after his father left, the family unit broke down. Pomale became involved with gangs, and - by the time he was 16 - in crime.

"You considered that your father had abandoned the family... Your family suffered financially as a result of your father's abandonment and you apparently considered you had a responsibility to provide money for the family," the judge said.

"You are not alone, Mr Pomale. A number of young Pasifika and Māori people feel such an obligation, as indeed do others, but they meet that obligation by working in paid employment in the community.

"The obligation is not met by engaging in crime to obtain money."

Justice Venning gave what he called a "modest reduction" in sentence for Pomale's personal circumstances, deducting six months from his jail term, which was set at 11 years.

However, Pomale took his case to the Court of Appeal, arguing that his sentence was "manifestly excessive".

His barrister, Marie Taylor-Cyphers, argued that a greater sentencing discount was warranted to reflect the information in Pomale's cultural report, and the three appeal judges agreed.

"His father stopped providing financial support for the family when Mr Pomale was 16 years of age, which resulted in considerable pressure to provide money to support his family's basic needs," the Court of Appeal decision said.

"This, rather than personal gain, was a major factor in him becoming involved in criminal activity, including drug dealing."

Considering the cultural report and other factors including Pomale's guilty plea and relative youth, the appeal judges quashed the 11-year jail sentence.

They imposed instead a sentence of nine years and five months.

- Ric Stevens, Open Justice