Electronic tagging operating in Northern Ireland since 2009

Twelve hundred people a year are tagged in Northern Ireland under rules introduced six years ago, with all bar 130 of them carrying the tags while they are out on bail. However, the system is used to ensure that people stay at the place where the court has directed they remain at night; however the tags are not used to track their movements by GPS.

Tags can be imposed as part of bail conditions or as part of early release terms. They can also be issued as part of a probation order or as part of penalties for juvenile offenders.

Private security firm G4S operates the system in the North. Tags are fitted around the individual's ankle. A monitoring unit is installed at the curfew address and is adjusted to receive a signal from the tag.

The tags are waterproof and shockproof and do not interfere with people’s normal activities – they can go swimming, have a bath and play sport. The tag looks like a sports watch and can be worn underneath socks or trousers.

Tags can only be removed if the strap is deliberately broken. The G4S control centre will detect immediately if a strap has been cut or damaged. Regular checks are carried out to make sure it is working.

The alarm is raised if a regular signal sent during the night from the tag is not received, which prompts a telephone call from the control centre, which demands to speak with the individual.

If the person wearing the tag is present and denies the breach, the equipment is checked for faults and repaired if necessary so that monitoring continues. The alarm is raised with the PSNI if they are absent.

Curfew order breaches are dealt with on a case-by-case basis, but it can lead to immediate arrest, a summons to court, a warning letter or a return to prison to finish a sentences.