On the contrary, it's very interested in the truth. When you want to present an expert witness, you include in the paperwork what truth they're going to tell the court, and their evidence for it.

The trial is a show for the jurors to convey information to them - everything that's going to be said NEEDS to be conveyed to the opposing side in advance, so they can prepare responses.

Surprise witnesses that blow cases wide open are only on TV.