 | "They're unreliable, and until these problems have been worked out, they should be withdrawn."
Dave Lyall, Swindon. | Josie with the controversial mobile speed camera |
Mobile speed camerasYour responses: "There is plenty of motivation for deliberate misoperation of these greed scameras."
Bernard Sheppee "Your story provides more evidence that the authorities are desperate to raise stealth tax through speed cameras."
David, High Wycombe "At last someone has stood up to these "infallible" devices - simple physics dictates these devices could give erroneous readings."
D. Hicks
Can the Camera Lie? Lots of people hate speed cameras, but Swindon's Dave Lyall has more reason than most. He was accused of doing 59 mph in a 50 zone, but was sure that he wasn't speeding.
Unusually, he went to court and showed the speed camera had got it wrong. Mr Lyall was found not guilty, the first time a court had upheld doubts about the reliability of these cameras. Inside Out first exposed a possible flaw with the mobile speed guns back in 2005. In our previous programme laser expert Dr Michael Clark showed how innocent motorists can be prosecuted for speeding.
It's a bit technical, but Dr Clark exposed a problem called 'slip effect'.
 | | Prone to error? How reliable are mobile speed cameras? |
Dr Clark looked at the possibility that if the gun's distance measurements start at the back of a vehicle and finish at the front, this could add the car's length to the apparent distance travelled.
Amazingly, this can add up to 30 mph to the recorded speed.
Back then, the UK manufacturer of the most common laser gun used in the UK, the LTi 20 20, told us it would be impossible to get a false reading due to slip on a moving vehicle.
But we also asked an engineering professor how easy it would be for an operator 500 yards away to miss the front of a vehicle with the laser beam and instead hit the side - where slip is more likely.
Professor Brignell from Warminster told us that just the movement created by pressing the trigger could result in a false reading.
Legal history Before our programme went out, several cases had been dropped by the Crown Prosecution Service but no drivers had ever challenged the cameras and won.
 | | Dave Lyall - groundbreaking legal case on mobile cameras |
Now Dave Lyall's case has made legal history. Together with his solicitor and Dr Clark as an expert witness, David fought his case at Devizes magistrates court.
Dr Clark said he believed Mr Lyall was the victim of a slip error which the gun's built in error trapping software didn't detect. Mr Lyall was found not guilty.
Laser gun Inside Out wanted to see if we could demonstrate Dr Clark's theory using an American version of the laser gun. Gareth Pritchard was also accused of speeding after being clocked by another type of Home Office approved laser gun.
 | | Dr Clark tests a mobile speed camera for accuracy |
Like Swindon's Dave Lyall, Gareth was sure he was innocent and challenged the fixed penalty:
"I know I was not speeding, I was not going to lose my license or anything, but just a question of principles."
Dr Clark was Mr Pritchard's expert. Unlike Dave Lyall, Gareth lost at the magistrates court - but he then appealed to the Crown Court and won. Now a higher court had agreed that the cameras can't always be trusted. Laser gun
Inside Out took Dr Clark to a test track to show how these cameras can lie. You have to see the results to believe them - click the "watch again" button from Monday January 22 on this web page.
Police Response
Meredydd Hughes, Chief Constable & Head of the
ACPO Uniformed Operations Business Area responded to Inside Out's findings as follows: "ACPO has complete confidence in the accuracy of all Home Office Type Approved laser speed measurement devices when used in an approved manner by a trained operator.
"The so called scientific tests we have seen in the media resemble a blindfolded child being given a precision rifle. They do not reflect the correct use of the equipment by a trained operator and are therefore misleading.
"The specific court cases mentioned all relate to cases where either the court did not accept the competence of the operator; or the prosecution did not have an expert available; or a procedural (i.e. administrative) error occurred.
 | | Police man using a mobile speed camera |
"No defence has yet succeeded in demonstrating that the equipment is inherently inaccurate, and we remain confident this will remain the case.
"Viewers of this programme might like to note that the lengthy, scientific and practical Home Office Type Approval process is administered by public servants - Police Officers, staff and scientists - who have no vested interests in the equipment, and are not seeking business from motorists - unlike the critics featured.
"We have often rejected equipment which has proved unreliable or inaccurate when tested.
"Since issuing further guidance to Police Officers and prosecutors, the opportunities for exploiting administrative errors have reduced significantly.
"All challenges to the accuracy of the equipment itself (we believe) have been defeated with costs to the defendants in some instances excess of £3,000.
"Home Office Type Approved Devices used for speed measurement have provided the Police service with a valuable and accurate road safety tool and the use of such devices has undisputedly influenced the speed of motorists which has in turn saved many lives."
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Inside Out - West: Friday January 19, 2007