Fear of perjury...

I'm contesting through written declaration (trial by mail). The cop clocked me at 90mph and cited me at 80mph.
I'm choosing not to mention that the cop actually SHOWED ME his radar gun. This is because I am going to express confusion at the ticket which says that the approx. speed was 80 but made some other note about 90mph under "code and section" (very hard to read). If I don't actually SAY that he SHOWED me the radar gun, is anyone going to be able to prove that he did? Am I in effect "lying?"

Well that isn't really the truth...

What difference does it make? If he clocked you at 90 and ticketed you at 80, he was cutting you a break. Instead of being combative, be thankful. He could have arrested you for criminal speeding.

You have to tell the truth in court or you could be held in contempt for perjury.

Don't worry about it. Go ahead and Lie all you want. No-one EVER gets convicted of perjury these days unless it is a blatant and major offense.

For example, I am a landlord and see tenants fill out rental applications full of lies all the time. The form states "under penalty of perjury" but I could not get a judge to even look at any case.

When I evict a tenant for not paying their rent they almost always file an answer with some lie or other on the court document. Again, the document states "under penalty of perjury" but when I go to court and win the case, the judge ignores the perjury aspect.

Politicians lie, police lie, lawyers lie, business people lie, homeless people lie so just accept it and join in.

hmmm...i would not lie.

If the cop showed you his radar gun while you were seated in your vehicle, you would do well not to lie. Police cars are equipped with cameras that pick up not only sound but video. So he informs the court he showed you the radar, and he presents his tape backup as evidence,

You're shooting yourself in the foot with your logic, as the cop was actually doing you a favor by writing 80 if he clocked you at 90. He could have arrested you for criminal speeding if you were going 20 mph over the posted speed limit.