A drug addict who supplied methadone to a teenage boy - who later fell into a coma and died - has been jailed for her "despicable act".

Eleanor Chatterton, 51, was sentenced yesterday to 15 months' jail for supplying the class-B drug to 17-year-old Hayden Smith.

When he died the teenager was about to join the Army.

Hayden was a friend of Chatterton's son and was at her West Auckland house in July 2008 when she gave him the drug in liquid from.

His father found him unconscious the next morning making the snoring noise people suffering from a methadone overdose emit. He was placed on life support in hospital but died.

Despite Hayden's having what was considered a lethal dose, medical evidence showed his death was due to liver damage, of unknown causes, that was unrelated to his consumption of methadone.

Chatterton was found guilty by an Auckland District Court jury of one count of supplying the drug but acquitted of a second supply charge. Prosecutor Scott McColgan said she had shown "no remorse" for Hayden's death and saw herself as the victim.

She was "grossly irresponsible" for supplying a harmful addictive drug to a young person, he said.

Her abuse of the methadone programme she used for help with an addiction to opiates made the irresponsibility "all the more greater".

Mr McColgan said Hayden had shown all the signs of a methadone overdose, irrespective of what ultimately caused his death.

"She gave this drug to a 17 year-old who was unfamiliar to it, who had not built the type of resistance Mrs Chatterton had."

The lawyer sought a jail term because home detention would mean she was back in the "very environment that festered this offending".

Judge Mark Perkins told Chatterton her offending was grave and her culpability was high. While Hayden didn't die from the methadone, he ingested a high quantity of it, he said.

"You must have known the consequences of supplying to a youngster," he told Chatterton, an "experienced" drug user who had 10 previous convictions for drugs.

Judge Perkins said giving it to him despite knowing the dangers showed a "moral weakness".

Chatterton's trial heard when that Hayden asked her what methadone was like, she replied: "It makes you feel strong and just gives you a good buzz."

Judge Perkins said the medical evidence proved that she couldn't be held accountable for Hayden's death - but supplying the drug was a "despicable act".

After the sentencing Hayden's father, Mike Smith, told the Weekend Herald that his son was just two weeks away from going into the Army when he died.

"That was the next stage of his life. He should still be alive. He was going to go in three months early but his mates talked him into not going, and he paid for it with his life."

Mr Smith said many teenagers experimented with drugs and alcohol but "not everyone is given methadone by their mate's mum". He wouldn't have allowed him to visit Chatterton if he had known what she was into.

Mr Smith described Hayden as a young man who was adventurous and into "soccer, surfing, everything".

"That's why she had no right, no right to do that."