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The jury in a trial of a man alleged to have wilfully ill-treated his stepchildren has heard he forcibly administered methamphetamine to his stepdaughter and her friend while they were as young as 14 years old.

The man, in his 40s, whose name is suppressed, is standing trial before Judge Raoul Edwin Neave in the Napier District Court after pleading not guilty to 17 charges which detail the abuse of his stepson, stepdaughter and her friend in fragmented time periods since March 2003.

Prosecutor Jo Rielly opened the Crown's case by telling the jury they would be hearing about a lifestyle, likely to be very different to their own, involving drug abuse and how it shaped the lives of several children under the defendant's care.

Yesterday the first complainant, who had known the man since infancy, told the court that he had injected methamphetamine into her arm and hands, as well as beating, raping and sexually violating her.

The court heard the woman grew up thinking the man was her biological father and had lived with the man and her mother in a Napier flat which "constantly" had drugs around; stashed in teddy bears, false bottoms of rubbish bins and walls.

She said she had once walked in on the man and her friend having sexual relations; telling the court her friend had been given methamphetamine and was "scared". The woman said he then proceeded to inject her with the drug too and the pair quickly became addicted.

Ms Rielly told the court the two stepchildren were exposed to an adult lifestyle, that the children were often asked to fetch drugs or guard the house while drug deals happened; all the while being told not to nark, not to go to the police and to do as they were told.

The woman described how the man's "evil eyes" would switch on when he was angry and testified she had once thrown herself between the man and her stepbrother as he was punching him and kicking him with steel-capped boots.

After receiving three blows to the head she told the court she woke up with next day in bed; her face swollen and covered in blood.

"It was always like walking on eggshells.

"You could just tell in his eyes before anything that he was angry and not to push that anger," she said.

The woman told the court that while she didn't like what he was doing she "tried to see the good" in him because he was her dad.

The alleged offending lapsed in 2005 after the man went to prison and it's alleged when his sentence ended he injured, sexually violated and supplied methamphetamine to the woman.

The man faces a total of eight counts of injuring with intent to injure, two counts of both wilfully ill-treating a child and administering methamphetamine and one count of sexual violation by rape, attempted sexual violation, indecent assault, assault with intent to injure and supplying methamphetamine.

The trial is continuing and expected to last three to four days.