I won't say he's wrong. John's car was going at 88km/h. However, the officer was standing in front of the car that is why in his eyes, John went faster.
The policemen's radar monitor shows 176km/h because it is the relative velocity. Therefore, the policemen saw my car in a different frame.
What John said was correct but officer, you were correct too. It is just the frame of perspective you are viewing the car. You see the car going faster than the original velocity because you stand infront.
I hope you realized that relative velocity and the velocity can be different.
That's why I saw you going faster because you were going towards me.