A leading UK NHS Trust has become the first to fit potentially dangerous psychiatric patients, including some convicted of murder, rape and paedophile offences, with GPS ankle devices that allows the authorities to track their position anywhere on the globe to within a few metres.

The South London and Maudsley NHS Foundation Trust told the press that the purpose of the scheme, which so far includes 60 or so medium and high-risk patients, is to stop them from absconding when they are on day leave or being transferred to and from hospital.

According to a Times report, the device at the centre of the scheme is the Buddi device, developed by Sara Murray, an internet entrepreneur who started the price comparison website confused.com, and others. The device has already been used to keep track of people with dementia.

Murray told the Times they started talking to the trust about the scheme early in 2009.

Under the scheme, the cost for each patient is £600, of which £250 pays for the device to be incorporated into a lockable steel-reinforced ankle strap that can only be broken with industrial bolt cutters. The device itself is approximately 2 cm x 5 cm x 5 cm and incorporates a mobile phone chip and GPS locator.

If the patient strays out of their defined area, the police automatically receive an alert giving their estimated position, personal details and photograph.

The scheme was approved for routine use after a pilot program that tested the secure version of the GPS locator completed in March. The devices are monitored by a private security firm in Yorkshire.

According to the Times, several other NHS Trusts are thought to be considering similar schemes using GPS locators.

Mental health charities have expressed concern that the ankle cuffs look like leg irons and could violate the rights of vulnerable patients.

Paul Jenkins, chief executive of the mental health charity Rethink, told the Times the devices were "demeaning" and patients with severe mental illnesses like schizophrenia should not be labelled as criminals. He said the scheme should be tightly regulated to ensure patients give their consent before being fitted with a device.

Jenkins said they would prefer to see money invested in better treatments rather than "wasted on demeaning items such as these". He said:

"Violence is not a symptom of mental illness and should not be regarded as inevitable."

The trust said they consulted with patients and their families. A spokesman told the BBC that they had a duty to promote public safety at the same time as providing high quality care for their patients.

"Our medium secure services provide hospital treatment for people with severe mental health problems - many of whom have restrictions placed upon them by the courts," he said, and confirmed that:

"We are currently exploring the use of a tracking system to help us provide safe, secure and effective services."

There have been several high-profile cases of patients absconding, fleeing abroad or reoffending, including that of 39-year old Terence O'Keefe, a convicted rapist who in March 2008, strangled a 73-year old man after escaping from a secure mental health unit run by the trust.

Sources: BBC, Times, buddi.co.uk.

Written by: Catharine Paddock, PhD