A teenage boy accused of killing Northland schoolgirl Liberty Templeman had to fend off repeated accusations of lying when he gave evidence in his own defence yesterday.

Tensions ran high in the High Court at Whangarei as Crown prosecutor Mike Smith cross-examined the now 16-year-old, who is alleged to have murdered and indecently assaulted Liberty on November 1, 2008.

The boy, 14 at the time of the killing, has name suppression.

His soft voice was in stark contrast to that of Mr Smith, who said the boy's story had changed "to suit your lies".

The boy had earlier given his account of what had happened on the day of Libby's death.

He said the pair had been walking over a bridge on Cobham Rd in Kerikeri when Libby saw a road cone in the water and wanted to go to it.

They followed a track through the grass towards the cone but while he was at the creek's edge, he slipped on a rock, knocking Liberty into the water, the court heard.

"She went down face first.

"She got up ... There was blood on her face and she was wiping it and she was crying. She was wiping her face with her hands."

He said he had tried to apologise to Libby. "I grabbed her arm and I turned her so she was looking at me and I said sorry. She swore at me and told me to leave her alone.

"I told her I was sorry, it was an accident, and she told me to leave her alone and I just kept trying to apologise.

"She said I pushed her over on purpose and now she has to go to New World soaking wet with blood on her hands and face."

Libby had told the boy to leave her alone, then punched him in the chest, the court was told.

"After she punched me I hit her back ... She kept hitting me and I kept hitting her back."

The boy said blood had been "bubbling" in Liberty's mouth, but he thought she was dead because it had stopped when he dragged her into the water to hide her under some bushes.

But Mr Smith disputed the boy's evidence, as he had given a different version of events during a videotaped police interview made about a week after Libby's death.

"At no stage when the detective spoke to you that Friday did you say she stopped breathing ... This is something else you made up?" he said.

In the video, which was played to the court, the boy said he was worried Liberty would go to the police after he hit her.

"So um, I strangled her, and I pulled her into the river where no one could find her, and pulled down her clothes so if they do find her it looks like a rape, or someone else."

Giving evidence himself yesterday, the boy admitted pulling up Liberty's top and bra and undoing her jeans and underpants to pull them down to her knees.

As he took Liberty into the river - "so that no one would see her if someone walked past" - she rolled over.

He went home, put his bloodied shirt in a bag and threw it out his window, then watched the movie Liar, Liar, he said.

The boy's lawyer, Catherine Cull, said the whole affair had been "a tragedy for everybody".

"It is not just a tragedy for the victim and her family, it's a tragedy for the accused, his family and the community as a whole."

She told the jury to keep an open mind and view the case dispassionately.

"This trial is not about the obviously devastating effect of the death of a young girl. This trial is about what the accused did or did not do, what he thought, and what evidence there is to establish whether or not he is culpable," Ms Cull said.

Defence and prosecution closing arguments are expected to be heard today. Justice Raynor Asher will then sum up the case before the jury retires to consider its verdict.

THE CASE:

Former Kerikeri High School student Liberty Templeman, 15, was found dead in a stream in Kerikeri on Sunday, November 2, 2008, 19 hours after she was reported missing.

THE ACCUSED:

A 16-year-old boy, then 14, was arrested in Kerikeri on Friday, November 7, 2008. He cannot be named because of his age.

THE CHARGES:
Murder
The Crown says the boy attacked Liberty, striking her, strangling her and dragging her while she was unconscious, leaving her face down in a creek to drown.

Indecent assault
The Crown says the boy lifted Liberty's bra and pulled down her pants and underpants to make it seem someone else had attacked her.