UPDATED 6.34PM A false police checkpoint set up by police to target euthanasia supporters is part of a police investigation into a suspected assisted suicide in June, police have confirmed.

LISTEN ABOVE: Human rights lawyer Michael Bott spoke with Chris Lynch about the incident

Wellington Acting District Commander Paul Basham also confirmed that further deaths are being investigated as part of Operation Painter.

"When we become aware of information that people are contemplating suicide, we can't look the other way," he said.

The police took the rare step of referring itself to the Independent Police Complaints Authority (IPCA) yesterday.

Police earlier admitted that officers used the pretence of a drink-driving stop in Lower Hutt to collect details about elderly people leaving an Exit International meeting last month.

Using those details, officers then visited the homes of nine people who were at the meeting to question them about potential involvement in assisted suicide.

Police called a press conference in Wellington this afternoon, where Basham said he wanted to "provide some context" to the controversial police actions.

He said a coroner advised the police that a toxicology report in August showed a person had died after consuming a Class C controlled drug.

The person was not suffering from a terminal illness and there were no signs that the death, which occurred in June, was suspicious.

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"Aiding and abetting suicide is the principal focus of the police investigation," Basham said.

Investigators had since identified several more suspected euthanasia cases, though police would not reveal the total number being investigated.

After the police became aware of the Exit International meeting, the drink-drive checkpoint was set up to collect details of the attendees. Nine people were later visited and given counselling and support.

Basham said the investigation and the checkpoint took place "in the interests of preserving life". Police were obligated to investigate serious offences "regardless of the strength of feeling on the issue." In an apparent reference to allegations of political interference - a law change around euthanasia is being considered by a select committee - he said police had no position on the issue.

Under questioning by reporters, he said the checkpoint was not planned in advance and was an example of police "thinking on their feet". 

He would not comment on the legality or illegality of the checkpoint while it was being reviewed by the IPCA. He also would not reveal who police took advice from on the unusual checkpoint.

Basham repeatedly underlined the seriousness of the case, telling reporters that aiding and abetting suicide was punishable by 14 years' jail. 

The district commander apologised, however, for an earlier police statement that committing suicide was "illegal" in New Zealand.

Basham said the comment was "regrettable" and clarified that only assisting suicide was an unlawful act.

Christchurch-based criminal barrister James Rapley said the case was a clear abuse of power and appeared to go against arbitrary detention and freedom of assembly rights.

Police powers in the Land Transport Act to stop people relate strictly to driving-related concerns, he said, and could not be used for any reason.

Rapley said the law also prevented police from asking for people's names and addresses unless they were checking whether a person had a driver's licence.

He cited the case of Hells Angels gang member Mark Ghent, who had a charge of obstructing police thrown out after he was arrested for refusing to give his name and details to a police officer.

"That's what they're really doing here. And they're asking normal people, not gang members, and who are entitled to go to a meeting."

Any potential search warrants or charges which resulted from police actions at the checkpoint were likely to be thrown out in court, he said.

Rapley helped to get charges thrown out in another case which involved a police ruse, albeit one in which an undercover officer was used. Drug charges against Red Devils Motorcycle Club president Roger Patrick and associates were dropped after police were found to have faked an arrest of an undercover officer to boost his gang credentials.

He said the checkpoint case threatened to damage public perception of police officers.

"Police need to be worried about this, because it is going to erode public confidence in them."

Barrister Michael Bott said just because someone was at the meeting doesn't mean they were wanting to commit suicide, or help someone commit suicide.

"It appears to be some kind of moral crusade, driven by someone on top, to stop people going to a public meeting to learn about exit and their goals."

Mr Bott said police used the breath-testing laws for something other than they're meant for.

"You've got a very limited power and it certainly seems to be an abuse of police at the checkpoints' powers."

- NZ Herald