At other times an expert will be used in the pre-trial stages, perhaps to give an affidavit supporting an element of the case. In other cases the expert may serve solely as an expert witness at trial. Sometimes an expert will play a combination of these roles. Lawyers tend to be generalists, not specialists in the specific field that may be at the heart of a case. The lawyer is not a cardiac expert, and would need to consult with experts in cardiac related medicine to review and understand the alternatives that were available for the proper treatment of the patient's particular condition.
Experts help explain the situation and the then available alternatives to the lawyer.
Other times experts will be used to evaluate the nature and extent of the damages sustained, the likely loss of earnings capacity and income a claimant has sustained, for use in settlement negotiations. Similarly DNA experts are regularly used in determining paternity. Experts may conduct a series of experiments to prove, or disprove a point. Assist in Case Development. An expert may be used to help the lawyer build a case, or defend a case.