How mobiles help: Mobile phone operators use techniques known as cell identification and triangulation to pinpoint the position of an owner's handset in cases of emergency.
Cell identification enables mobile operators to determine which base station transmitter a particular handset connects with when it is switched on. A handset that is switched off will not connect to a transmitter and therefore provides no signal to track.
Firms measure the strength and direction of a radio signal that connects a mobile handset from a base station to give a general idea of where a handset is located. But in many areas more than one base station will receive a signal from a mobile, enabling the firm to use a process known as triangulation to give a far more accurate location for a mobile.
The operator is able to use its network management systems to measure the strength of a signal received from three or more transmitters.
It then analyses the signal data and the direction of each signal to provide a location.
The accuracy of triangulation depends on the amount of base stations in a particular area and is often generally only to within 200 metres. Urban areas usually provide better accuracy because of the number of transmitters. However, buildings and hills can distort signals, making accurate readings much more difficult.
The Garda can use these two techniques to track criminals and there is a suspicion among firms that gangs or terrorist groups have been responsible for sabotaging mobile masts in certain areas.
However, pre-paid mobile phones - which protect the identity of an individual - are commonly used in criminal activity.
None of the mobile phone companies would comment yesterday on the methods they can use to track phones. But there are new positioning technologies emerging that are likely to be used shortly by operators.
A much more accurate positioning technology that is already available in some handsets, outside the Republic, is GPS chips.
These chips act as receivers that pick up radio signals sent from satellites to determine the location of a mobile handset, military equipment or a vehicle such as a taxi.
The GPS system is made up of 24 satellites equally spaced about 20,000 kilometres above the earth which transmit two coded signals, one of military use and one for civilian use. The system is much more accurate than triangulation - to within about 10 metres - but it relies on receiving a clear signal from the satellites.
Mobile operators are currently evaluating whether to embed these types of chips into handsets, as they could be used to deliver a range of location-based services.
These are services that identify where a particular mobile user is located to offer them accurate directions to a particular location such as a restaurant.