Whether CCTV cameras are an unwarranted intrusion into the privacy of citizens going about their lawful business or a deterrent to crime depends on how the information gained is used.

That the number of publicly-owned CCTV cameras has tripled over the last 10 years suggests growing faith in their value as a deterrent -- the electronic equivalent of the watchful eye of the good neighbour.

The first cameras, strategically placed to monitor areas where trouble occurred, however, had the effect of displacing anti-social behaviour and assaults out of range of the camera. One of the main reasons for the increase in their number is to overcome that limitation.

The idea that only those who have something to hide have anything to fear from CCTV underpins its use and gives rise to the idea that cameras should increase a general sense of security. Yet the proliferation of cameras on streets and both inside and outside public buildings and increasingly in private and commercial buildings can have exactly the opposite effect, acting as an ever-present reminder of the threat of crime or even terrorist activity increasing the fear of crime.

Just as damaging is a false sense of security where cameras are useless because they have been switched off, have no film or are not monitored and recognised as an empty threat by those intent on anti-social behaviour.

Statistics, such as the one which shows the Western Isles as having the highest number of CCTV cameras per 1000 residents in the UK - largely as a result of having cameras attached to schools with very few pupils - can be misleading. It is more important to analyse how effective the cameras are. CCTV images provided significant evidence in two recent murder trials in Scotland, substantiating the claim that if they do not deter crime they can help to solve it.

It is time for a review of what we want to achieve from the use of CCTV and how effective it is, not least because Scotland now has more than its fair share of electronic eyes. Five years ago Richard Thomas, then information commissioner for England and Wales, warned that Britain was in danger of “sleepwalking into a surveillance society” if data from identity cards was linked with information from monitoring devices such as CCTV cameras. That would undoubtedly turn Big Brother from a protective to a threatening entity and must be resisted.