The trial of the man accused of murdering British backpacker Grace Emmie Rose Millane in December last year has begun.

The man, 27, who has name suppression, denies a single charge of murder at the High Court at Auckland.

Grace, 21, died before on or before her 22nd birthday between December 1 and 2 last year in Auckland, while travelling on her OE.

The accused stood in the dock clean shaven, wearing a navy suit and a black shirt in courtroom 11 at the High Court.

On Monday, a jury of seven women and five men were empanelled with Justice Simon Moore presiding over the case.

Before the 12 jurors were selected, Justice Moore told the jury pool that anyone who participated in public marches and vigils held for Grace after her death would not be allowed to serve on the jury.

"Her disappearance, followed by confirmation of her death excited intense media attention both here and overseas," Justice Moore said.

"Vigils were held across the country ... politicians and significant others waded in to the debate ... the story took the nation by storm," he said.

Justice Moore said it was important for a jury to have an unbiased mind and not be swayed by feelings of sympathy and prejudice, but to reach a verdict "cooly and dispassionately".

The Crown is expected to call 36 witnesses including Grace's father David.

Auckland Crown Solicitor Brian Dickey heads up the prosecution team alongside co-counsel Robin McCoubrey. The Crown is expected to make its opening address to the jury on Wednesday.

An opening statement may be made by the accused's defence lawyer Ian Brookie or Ron Mansfield.

Senior police officers including Detective Inspector Scott Beard, who was in charge of the case, were seated in the front row on Monday.

A number of members of the public were also sat in the public gallery as well as a media contingent of about 20, with both New Zealand media and overseas media.

The search for Grace was sparked by her parents who became concerned she hadn't been in contact with them since December 1.

This was unusual as she kept in touch with them and other family and friends daily, they said.

The family was especially worried as she hadn't responded to messages they sent to mark her birthday on December 2.

Checks at the Base Backpacker hostel on Queen St where she was staying revealed she hadn't returned there after her Saturday night out.

An appeal for sightings of Grace was made by Auckland City Police on December 4, who issued a photograph of her wearing a black baseball cap.

More than 18,000km away in her home town of Wickford, friends and family frantically began spreading word of her disappearance.

On December 9, Grace's body was found buried in the Wāitakere Ranges.

The trial is expected to last between four and five weeks and will continue on Wednesday.

-Stuff/Catrin Owen.