A United States citizen has been charged with helping a woman from Auckland's North Shore woman to commit suicide.
The charge of assisting suicide was laid on Friday, after police in Auckland finished investigating the death of Audrey Wallis in 2007.
An arrest warrant has been issued for a 48-year-old woman who lives in North Carolina.
Detective Sergeant Scott Armstrong says New Zealand police have been helped in their investigation by Interpol and US federal agencies.
He says there is no way of forcing the accused to return to New Zealand to face the charges, because the offence of assisted suicide is not covered in the country's extradition treaty with the US.
Detective Sergeant Armstrong says the accused has turned down an offer to return at no cost to herself.
He says investigators did consider laying more serious charges, such as murder charges, which would have come under the extradition agreement.
