证据必须在出庭前双方都看过，不能打伏击。

"but if it is intended to contradict the witness by the writing, his attention must, before the contradictory proof can be given, be called to those parts of the writing which are to be used for contradicting him; "

https://www.youtube.com/watch?v=I6pUa5dOq1A

The movie "My Cousin Vinny" is a terrific accurate dramatization on how legal evidence work in courts.  You should take a look.