In these circumstances I would say that you cannot be found guilty. For a successful conviction, speeding requires corroborative evidence.
So in normal circumstances, the laser gun provides the primary evidence, and the police officer provides the corroboration.
The same applies to speed cameras. The speed detection device provides the primary evidence, and the white lines on the road are for corroboration.
In your case, the only evidence available is from the police officer. Corroboration is required by law for a conviction. So I can't see it going anywhere.