Expert Witness Role, Report Writing, and Testimony
Admissibility and the gatekeeper
Expert testimony must be relevant and reliable. Under Daubert (federal and many states), the judge assesses whether the method is testable, whether it has been peer reviewed, its known error rate, and its general acceptance. Under Frye, the test is general acceptance alone. Experts may rely on facts and data of a type reasonably relied upon by experts in the field, and may be cross-examined using learned treatises. The LNC must distinguish fact testimony from opinion testimony.
Writing the report
A defensible report states qualifications, materials reviewed, assumptions, methodology, each opinion, and the basis for it, expressed to a reasonable degree of nursing or medical certainty where required. Keep opinions within scope: a nurse may opine on nursing standards, documentation, and care delivery; medical causation and diagnosis usually require a physician. Cite records precisely. Avoid advocacy language, speculation, and conclusions unsupported by the record. Disclose fees, prior testimony, and publications.
Testifying
Deposition and trial testimony reward preparation: answer the question asked, do not volunteer, concede what is true, and distinguish inability to recall from not knowing. Expect attacks on qualifications, bias, and consistency with the report. Testifying experts generally must produce their file, and certain communications with counsel may lose protection.
Traps: assuming a bare conclusion survives challenge without a stated basis; confusing Daubert with Frye; assuming a nurse can offer medical causation opinions; drifting from consultant into advocate.
Rule of thumb: for every opinion, be able to state the record page, the standard relied upon, and the reasoning in three sentences or fewer.