Dr Phillip Tann was able to use information from a tracking system he is developing to prove he was driving under the speed limit after allegedly getting caught driving at 43mph in a 30mph zone.

Police say the cameras they use are perfectly safe and accurate, but Dr Tann claimed his invention showed he was doing 12mph less than officers claimed.

"I knew when I received the fine I couldn't have been exceeding the limit because I'd seen the van with the camera so I was surprised to receive a fine.

"The cameras used are not 100 per cent accurate, but my system is," he said.

Paul Biggs, of the Association of British Drivers, said every week motorists were successfully challenging fines issued after they were allegedly caught breaking the speed limit.

He claimed cases were usually discontinued because police and the Crown Prosecution Service (CPS) did not want to set a legal precedent.

"They shouldn't be used to just target a car. They are supposed to have some prior suspicion first," he said.

Mr Biggs claims cameras can slip, and also pick up reflections from cars driving on another carriageway, which can lead to inaccurate readings.

Dr Tann was driving through the city collecting road information for his new tracking system in November last year.

The scientist, who quit his full-time job as a lecturer at Sunderland university to work on his gadget, said he noticed he had been clocked by a police mobile speed camera but didn't think anything of it as his device showed he had been driving at only 29mph.

But then Dr Tann, from South Shields, received a letter and fine from Northumbria Police.

Sure of his innocence, the scientist, who has spent the past two years working on his new Autopoietic tracking system, similar to an aircraft's black box, decided to challenge his penalty in the courts.
Dr Tann, who owns Birtley-based business Autopoietic Systems (Tann Ltd), said: "When I received the fine, I checked the database.

"The system I was testing is more accurate than anything else on the market and it said I was only doing 29.177196 mph at that time."

Dr Tann presented himself before magistrates armed with a CD he said contained evidence proving his innocence and pleaded not guilty to breaking the speed limit.

Dr Tann said the CPS requested to view the system and later his prosecution was dropped – which he claims is because the data from the device proved the police camera wrong.

However, the CPS claims the prosecution has now been discontinued because the officer in charge of the camera had since left the force and could not attend the court case.

A spokesman for the CPS confirmed Dr Tann's case had been discontinued, but denied it was because of errors found in the evidence.

He said the CPS had written to Dr Tann's solicitor and made clear it was down to the officer who had been operating the equipment leaving the force.

Northumbria Police said they were satisfied the camera reading was accurate and maintained the case was discontinued for "administrative reasons."