The signal of a mobile phone can be used to work out the approximate location of a phone. It is much more accurate in an urban area, where there are many more masts, than in the country. The phone companies collect this information and it could be used by the police or in court. However, it is the location of the phone not the user. The police would also need to prove that a particular person actually had the phone with them at the relevant time.I suspect that in practice the mobile signal is very useful for detection, ie finding a criminal or a missing person. But it would not be very good as evidence in court because it would be very easy for the defence to disputes its accuracy. Mobilspionage