When to Use an Expert Witness
When an attorney uses an expert witness, they have a plan well in advance at the trial. Discovery control orders and the rules of civil procedure require that experts be disclosed ahead of time, often many months before trial. The disclosure sometimes requires their opinions, if nothing else, and certain courts require actual accident reports be produced to the other side many months before trial so the evaluation process can occur and depositions can be taken.
Using an expert during trial is limited only by the creativity of the lawyer. It is usually most effective to have the expert as a teacher to inform the jury how the expert came to their opinion, how the methodology is reliable, and why the steps taken are essential. The best experts get excited about teaching others why their science or discipline matters to the case at hand.