What actors and actresses appeared in Der Mitwisser - 1989?

You're likely thinking of the German film "Der Mitleidige" (The Compassionate) which was released in 1989. There is no film called "Der Mitwisser" with that release date.

The cast for "Der Mitleidige" (1989) includes:

* Mario Adorf as Professor Max Kramer

* Alexandra Fechter as Lisa

* Bruno Ganz as Dr. Paul Steinhof

* Armin Rohde as Robert Kramer

* Ruth Maria Kubitschek as Anna Kramer

* Günter Lamprecht as Judge Dr. Werner

If you're interested in a different movie with a similar title, please provide more information.