In The Attorney-Expert Relationship: Unraveling the Complexity, Peter T. Tomaras writes on his experience as a premises liability expert witness regarding setting parameters:
When attorneys call, experts must determine from a brief description if the case falls within our span of competence and is ethically feasible. Frequently, attorneys ask us to make a preliminary assessment. That’s not readily doable–or prudent. Attorneys may ask, “Do you think I have a cause of action, here?” Well, perhaps; but no expert should offer an opinion at this stage, nor should we hear any confidential information. For me, the best starting point in determining the merit of a case is reading the petition or complaint (if it has been filed) and, if available, the answer to it. But some attorneys seem reluctant to forward the complaint, let alone pay an expert to review it, who then might pass on the case.
Some advance work can lower this hurdle. Before calling potential experts, attorneys should check their credentials and references to verify that they are both competent in their fields and, above all, have a reputation for integrity. Then, if an attorney wants an expert’s early reading as to the case’s strengths and weaknesses, he or she should be willing to pay a reasonable fee for this. If the expert’s screening suggests a weak case, the attorney cuts losses; if the expert feels he or she can espouse a supportive opinion, the attorney can confidently retain the expert. Either way, the nominal investment is justified.