I doubt it, proof or evidence is for a court. If the Garda stopped you and informed you that he observed you driving over the speed limit then you have two choices, either pay the fine or go to court and dispute it. The Garda would then back up his claim with proof in the court.
Demanding to see proof is not what being stopped for speeding is all about. You could of course say you did not believe you were driving too fast and apologise for you lack of attention and control. The Garda stops you as you are a danger to other road users, to inform you of your poor behaviour, and to fine you so as to create a deterrent all in the hope that you correct your behaviour and drive safely in the future.