Teenager Christie Marceau was held at knife point and told she would be stabbed if she didn't follow orders from the man who is alleged to have later murdered her.
Akshay Anand Chand appeared at the High Court at Auckland today where he pleaded guilty to charges of kidnapping, assault with intent to commit sexual violation and of threatening Christie with grievous bodily harm. The charges were laid in September last year.
He also faces a charge of murdering Christie two months later but has not entered a plea on that charge.
Crown prosecutor Simon Moore SC indicated Chand's lawyers would be arguing a defence of not guilty by reason of insanity.
Details of the earlier kidnapping charges were revealed in court today by Mr Moore as he read the police summary of facts.
Chand and Christie went to the same primary school and met up again in their teens while working at the local supermarket.
The court heard how on the morning of September 6 last year, Chand called Christie and demanded she come to his house or he would "hurt himself''.
Chand hid a kitchen knife in the waistband of his trousers before Christie arrived.
The pair sat in the lounge room and Chand began talking about his "personal issues''.
He began to get agitated and demanded Christie hand over her cell phone before pulling out his knife.
He told her: "If you don't obey me, I will knife you, if you scream, I will knife you, if you try to escape, I will knife you.''
Chand demanded that Christie take off her clothes and threatened her again. She stripped down to her underwear.
He continued to talk about his problems for about 35 minutes before he allowed Christie to put her clothes back on and leave.
But before she left, Chand told her he would kill himself when she had gone.
Christie told a family member of the threat.
Chand later told police that he had planned to rape Christie but didn't go ahead with it.
Chief High Court judge Justice Helen Winkelmann remanded him in custody and he is due to be sentenced next month.
Christie's family, supported by the Sensible Sentencing Trust, were in court for today's hearing.
They have been campaigning for tougher bail laws, and made a verbal submission at a Law and Order Select Committee last month.
Chand was arrested and remanded in custody last September on the kidnapping charges but after several court appearances he was granted bail on the condition that he lived at his mother's house, only a few streets from the Marceaus' home on Auckland's North Shore.
He was also placed under a 24-hour curfew and ordered not to leave the house unless
he was attending medical or legal appointments and was accompanied by one of two specific adults.
Two months after the kidnapping, Christie was fatally stabbed and died in her mother's arms.
Police found Chand at the property, and he was later charged with murder.
Speaking through tears, Tracey Marceau told the select committee that the day Christie died had destroyed her life.
"On November 7 2011 my heart shattered and my life changed forever. You cannot save my baby Christie, or me. But you can help the people of New Zealand,'' she said.
The committee also heard from others involved with Christie's Law, which was backed by a petition containing more than 60,000 signatures from people across New Zealand.