I believe that expert witnesses should not be paid. The main reason for this is the fact that being paid for a testimony can be considered, in some cases, to establish a responsibility towards the person who is paying for the services. This can make the expert act in a biased or less objective way, which defeats the purpose of his work.
The most important person in the courtroom during a trial is the person who is on trial. The defendant is the reason why the trial is taking place, and why the rest of the people have gathered in the courtroom. Moreover, the defendant is the person who would be most affected by the outcome of the trial.
