The Whole Truth

The argument used to be that the camera never lies, but when it comes to evidence that will stand up in court, even industry experts now say the 4.2 million cameras in the UK do not give the whole picture.

CCTV has come to be seen as a magic bullet, but its effectiveness can be undermined by everything from the age of the equipment, through the positioning of the cameras, to something as simple as the number of times the tapes recording the pictures have been re-used.

Anyone who ever owned a VCR knows how a tape used to record a favourite soap week in, week out, would result in well-known actors becoming increasingly less identifiable as the picture quality declined with each successive recording.

"Fragile" Recordings

It is this problem that seems to be uppermost in the mind of the police as studies are made of CCTV footage in the hope that light can be shed and evidence gained against perpetrators of crime.

CCTV cameras may be far more commonplace in Britain, but many in small businesses such as corner shops and petrol stations still rely on similar analogue tape, according to industry insiders.

Peter Fry, Director of the CCTV User Group, which represents more than 500 organisations using the cameras from hospitals to councils, says: "Everyone expects far too much out of CCTV."

One of the organisation’s members, who works for a major police force in England, gives the figure of 80% of the images he is asked to examine as being "totally useless" when it comes to relying on them as evidence. The problem is that a single tape is often used to record the pictures from multiple cameras – producing an image that is a fraction of the size of the actual TV screen.

Even with digital systems, where the individual feeds can be separated off, some recorders store too little information for the picture to be blown up to a useable size before the image disappears into a mass of dots – a problem all too familiar to anyone who has ever tried to zoom in on a picture on their computer screen.

Poor Quality Images

Much of the equipment being sold was never intended for such commercial use and comes from home entertainment manufacturers looking for new markets. Also the material cannot be downloaded to another format such as DVD and that means the police have to remove the entire hard-drive as evidence.

Digital technology has meant a huge leap in the number of images that can be stored. But that in itself has become a problem. Officers investigating the 7/7 London bombings went to seize material from one local authority to be confronted by a stack of DVDs 16 feet high, according to one insider.

Wrong identification

Even when high quality images exist, and more importantly are located by detectives who have studied hundreds of hours of CCTV, questions remain about how useful they are at actually identifying suspects.

Academic research has shown that when people were given a still picture of somebody and asked to pick them out of a series of CCTV stills, they picked the wrong person or could not find them at all in 30% of cases – and that was when the two pictures were taken in identical lighting conditions with the subject displaying a similar facial expression.

Better quality images from newer digital systems have the potential to make CCTV more useful in court, according to Michael Bromby of the Centre for Forensic Statistics at Glasgow Caledonian University. But he also sounds a warning.

"If you get a DVD and stick it on your telly then it can do all sorts of things to the person’s face before it decodes the signal properly and that’s where you’re working with a limited number of broadcast standards. You have to accept that the camera and computer are doing something to compress and store the image which can alter it. And that matters where somebody is saying this is or isn’t the person, when you look at the ratio of the distance between their eyes or from their nose to the chin," he explains.

Right Place

Before the lawyers and experts can even begin those arguments though, the camera has to capture an image.

The case of Annie Freeman, an 87 year old pensioner ordered to remove her hat when she popped into a pub in Aldershot so as not to hide her face from CCTV cameras, shows how it does not take hi-tech tricks like those used by crooks in the film Ocean’s 11 – to foil the security systems.

More often though, it comes down to the cameras simply not being in the ideal place. Dr Andrew Adams of the University of Reading cites the case of a colleague who is working on cameras designed to spot potential terrorists, who had his car broken into on campus.

"Within 20 minutes he went to security staff with a description of some youths he’d seen hanging around the car park, only to find that despite all the signs warning of CCTV surveillance, not one had been pointing in the right direction to catch the suspects."