Potentially dangerous psychiatric patients are being fitted with GPS tracking devices to prevent them absconding on day leave. The South London and Maudsley NHS Trust has attached the £600 ankle devices on more than 60 medium and high risk patients under the pilot scheme. The trust said it had consulted patients and families. The devices, which can track a person's location to within a few yards, are already used for dementia sufferers. They came into use in south London after rapist Terence O'Keefe, 39, escaped from custody at King's College Hospital before strangling 73-year-old David Kemp.