Police are using restraint boards to strap down high-risk prisoners, with the support of human rights groups, as long as they use them properly.

The boards, which have chest, arm and leg straps and a built-in pillow to protect the back of the prisoner's head, can contain those who pose an extreme threat to their own safety. Twenty-seven boards are in use in stations from Whangarei to Invercargill.

Police national headquarters operations and projects manager Inspector Tom Ireland said the boards were introduced because other restraints were "falling short".

When someone under the influence of P or having a psychotic episode was flailing around, handcuffs and leg restraints were not enough to contain them and keep them safe, he said.

"Once they [prisoners] are in the cell they can do significant damage to themselves, running into things, striking their heads against the wall.

"We needed somewhere to immobilise them. Calling a doctor in for medical restraint was not an option because you don't know what substances [the prisoner] has taken."

Ireland said the boards were not there as a punishment or to protect police officers.

"They have to be authorised by the shift supervisor, the person must be constantly monitored and they must be released from the board as soon as the rational reason for the restraint has passed."

It takes five staff to get a person on to a board. Recent examples of the board being used include a morbidly obese man with the mental age of a 7-year-old who became extremely violent, then lay down and refused to move.

Another man was suicidal, violent and refused medical treatment. Ireland said he kept trying to "interfere" with a deep wound on his face.

"Putting him on the restraint board was the only way to prevent him from causing harm to himself. "

The boards were tested for three years in Christchurch, after police informed the Independent Police Complaints Authority, Amnesty International and the Howard League for Penal Reform. There have been no complaints about them.

Howard League spokeswoman Kathy Dunstall said the boards needed to be carefully monitored.

"There's always a risk they will be overused or used to restrain someone that's simply annoying police.

"Clearly police have to deal with really difficult situations and people with mental health problems. "

Council for Civil Liberties spokesman Michael Bott saw the need for limited use of the boards.

"You don't want people to self-harm when they are not in a state to make decisions for themselves. There is a risk, though, that they can be used improperly."

Police Association vice-president Stuart Mills said feedback had been positive.

"There was an incident last week in Henderson where it was very effective in dealing with a very aggressive and agitated man attempting to harm himself."

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