driving offence, page-10

re: driving offence - tradein Police car was mobile and I assume he caught me him driving. I do not know it was radar or lidar. His infringement notice reads radar/lidar penalty notice. I saw only speed 134km on his gun screen. It was m4 motorway and was quite busy in 1st and 2nd lanes. I and the police car were in 3rd lane. I was driving on the limit 110km zone; may be little more but definitely not 134km.
Can a police car catch our conversations; isn't it against privacy policy? Though I did not utter any abusive language. Can I challange officer to produce that dialogue in court? Thanks for help..