Two Melbourne drivers have beaten speeding fines by challenging camera images in court, and more are set to follow.

John King and Claus Salger won David-and-Goliath battles against Victoria Police by using information contained in a speed camera operator's manual.

Illustrations in the manual, obtained through Freedom of Information, proved they could not have been speeding.

In November, a Melbourne court will hear a challenge to a speed camera fine on the same basis.

Barrister and traffic law expert Sean Hardy will call two experts in the Melbourne Magistrates' Court on behalf of a client who says he was not speeding.

Mr Hardy said Mr King and Mr Salger had exposed systemic problems in mobile speed cameras and the case would test if their success could be repeated.

"I don't think John and Claus have blown the system apart," Mr Hardy said.

"But I think they've exposed cracks in it. And people have been exposing cracks in it for a long time."

Mr King and Mr Salger won court costs from Victoria Police in separate prosecutions and say their cases reveal a culture of secrecy, misinformation, cover-up and sloppy prosecution.

They said the system of verifying images was flawed and biased against drivers.

The men claim the system is so complex and secretive most drivers cannot challenge their fines.

"Most people aren't going to spend three days in court fighting a $160 fine," Mr King said.

"I was able to win my case using their own operator's manual. It showed the camera didn't produce an accurate image in my case."

Mr Salger, who has 45 years experience in radio electronics and worked for 16 years at Melbourne airport, picked apart the camera manuals and studied the complex radar science that defeats most drivers.

Tests proved that radar-activated cameras can be triggered by street signs, road barriers and even the movements of car aerials, he said.

"As the system stands now you don't have to have committed an offence to be guilty of it," Mr Salger said.

"The camera does not point and say, 'this car did it, or this one did not, or none of them did it'. It takes a picture.

"And then that picture has to be interpreted. The flaw I see is in the interpretation.

Under Victoria's speed camera legislation police normally only have to prove the camera was properly set up and calibrated in order to obtain a conviction.

One of the men's claims that is hotly disputed is that speed camera infingements are computer generated by Tenix, the camera operators.

Mr Salger and Mr King say the system simply identifies a number plate, searches for the owner of the vehicle and sends out an infringement notice.

In March this year Mr King had his speeding case dismissed and was awarded $1260 costs in Heidelberg Magistrates' Court.

Mr King's expert witness was Mr Salger who beat a speeding offence at Broadmeadows Magistrates' Court in 2006.

It took Mr King 18 months to prepare a defence because of the difficulty of obtaining the speed camera manual that helped him prove he was not speeding.

Magistrate Roger Franich said the Tenix employee who set up the camera described the manual as his "bible".

However police witness Chris Burden, an engineer from RMIT who calibrates all Victoria's speed cameras, dismissed the manual.

"Burden said the manual used by Tenix operators was full of technical errors," Mr Franich said.