“The name ‘Demux’ comes from ‘de-multiplex’", he says, “and basically means to un-muddle. My job is to clarify CCTV images so that they can be used as evidence, either for the prosecution or the defence."

In fact, Demux is one of only two companies in the country – the other being in Manchester – which can de-multiplex a video tape of up to sixteen CCTV recordings in “real time". Dave explains, “When you play a video like this, it looks very confusing because you have umpteen camera angles played very fast one after the other. What I do, in one go, is to separate these images so that you end up with one continuous recording per camera." At the same time, Dave can make a working copy of the original tape so that degradation of evidence is kept to an absolute minimum. In normal circumstances, the tape would be copied and rewound many times – once for each camera recorded – and this would result in a stretched tape and a reduced quality of picture.

Before starting Demux in March 2004, Dave was a policeman for eleven years. During one investigation, he was given (in the words of the prosecution barrister) “the bed of nails task" of analysing hours and hours of multiple CCTV footage. Dave admits that it was a very steep learning curve, but he discovered he had a fascination and natural flair for this type of work. Over the years he has painstakingly produced time-lines and story boards, sometimes up to 300 pages long, detailing suspects’ routes, actions and meetings. In many cases, the evidence has proved very important.

For example, when Demux recently assisted Northamptonshire Police, Dave was able to clarify some CCTV footage to such an extent that eight people came forward on the same day to name the same individual. This man was subsequently charged with a very serious assault upon an elderly lady. As well as having the satisfaction of knowing that a suspect had been successfully identified, Dave has potentially saved the Northants police force an enormous amount of time, money and manpower, since they were considering using BBC Crimewatch and conducting a voluntary DNA sweep of the surrounding area.

Dave also analyses infra-red images, as these can be misleading. Dave comments, “Natural and man-made fibres reflect this type of light very differently – dark tones or colours can appear quite pale – and naturally this could have serious implications if a suspect’s clothing was wrongly reported."

Mention the TV programme “CSI" and Dave rolls his eyes and sighs deeply! “You have to understand the difference between fact and fiction," he says. “I can only clarify the image that’s there. I can’t zoom in on a victim’s eyeball and extract the reflection of the offender from it. If only that were possible!"

“It seems to me that juries nowadays are almost disappointed sometimes because their expectations have been raised so high, and the reality of what’s possible actually comes as a bit of a let-down," he adds.

Dave has worked for many police forces, solicitors, barristers and security companies, but he is also keen to try and develop Demux’s health & safety applications. “Operations managers have huge responsibilities and we could help them to ensure, for example, that the correct protocols are being followed when it comes to manual handling or fork-lift truck driving using their own CCTV system" he says. “We live in an increasingly litigious society, so I think our services could prove extremely valuable."