Failure analysis expert witness examined a failed hospital chair. The chair failed during a breast X-ray examination. The chair had been altered 3 years prior to the failure, and the machine shop that had made the alterations was accused of causing the fatigue failure. Examination of the chair discovered hammer marks on a critical region of the chair. The chair owner had performed repairs two days prior to the accident. The nature of the repairs was such that the hammer marks would have been appropriate. Therefore, the failure was attributed to user error. This fatigue fracture was not the result of a product defect. Therefore, product liability was not in question.