A "wilfully blind" woman became entangled in her brother's Thai Bandidos drug operation which led to $17 million worth of methamphetamine imported into the country, and $350,000 of jewellery and cash seized.

Queenie Anne Matthews, 59 and Meinata Piahana, 29, were sentenced today in the High Court at Auckland to three charges each of importing or attempting to import packages of methamphetamine into Auckland between September 2015 and September 2016 via the international mail system.

Further charges were dropped following Operation Cossack, a seven-month investigation by Customs and police.

Matthews had helped her brother and co-accused Adrian Le'Ca, 56, who entered guilty pleas to importation in 2016, possessing 14.9kg of methamphetamine, and 1.9kg of cocaine. Five other charges against him have been dismissed.

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"She was wilfully blind as to what was in the packages. She deliberately didn't ask Mr Le'Ca," Matthews' lawyer Samuel Wimsett said.

Piahana is also Le'Ca's nephew.

Le'Ca returned to New Zealand in September 2015, after six years in Thailand and 15 abroad where he is said to have developed ties to the Bandidos, the court heard.

He will be sentenced later this month, while a friend of Le'Ca was sentenced earlier this year for his part in the operation.

At the time of the arrests in October, 2016, police said about 17kg of methamphetamine, $150,000 of jewellery and $200,000 cash had been seized.

Police said the drugs had been imported with the help of the Thailand chapter of the international Bandidos gang.

Matthews, who has breast cancer and "serious physical health challenges", has shown a relative lack of concern with her own wellbeing since the offending and is worried about her family and grandchildren, Wimsett said.

Justice Ailsa Duffy said Matthews' case was "uniquely tragic".

"Without that [family] connection I'm sure that none of you would be before the court for sentencing today," the judge said.

Justice Duffy said meth was an "insidious, pernicious and highly addictive drug" and has horribly affected Matthews' family.

She sentenced both Matthews and Piahana, who were well supported by family in court, to home detention.

About 17kg of methamphetamine, with a street value of $17 million, was seized during Operation Cossack. Photo / Supplied
About 17kg of methamphetamine, with a street value of $17 million, was seized during Operation Cossack. Photo / Supplied