That is precisly why I brake and switch the jammer off as fast as is safe. picture this in court:
Officer, did you get a speed reading? Yes on the second attempt.
Is my car fitted with a jammer? Yes
Is the jammer working? No
Could it be turned on? No
Can you prove the jammer was on at any time? No
Then going back to the first question, if I was jamming you, would you have got that second speed reading? No, maybe.
Plenty reasonable doubt.
As mentioned earlier, laser jammers are not illegal to own or use (not yet in goverment legislation), however they get you for obstruction of justice here, which is a very diffrent matter to prove. Why when he wanted to fine me for having it and I asked him to show me the goverment gazette showing where they are banned did he say I may be right I can go? I believe they prey on the uninformed.
A case in point, I was once pulled over for speeding when a traffic cop caught me at 1200m and wanted to fine me R800 ($120). When I asked him "But isn't the law a maximum of 400m?" He just let me go. That law has now been updated to 500m. It was this encounter that saw me buying my first laser jammer as it was the first time I had ever been 'caught' by a laser gun.