Expert medical opinions are necessary in pretrial cases and other legal matters. They act as means of evidence for administrative bodies and courts. It may be necessary to adapt the method of evaluation depending upon the issue or subject matter to be evaluated. We report on a social court case, which needed to answer the question of the medical necessity of a functional electrical stimulation orthosis prescribed to improve the function of a drop foot accompanied by an atactic gait disorder. The claimant suffered from a stroke, which had occurred several years before. Her aids were an ankle-foot-orthosis for foot lift and a wheeled walker. The current treatment was to be augmented by the disputed device. The statutory health insurance declined to meet the costs. They failed to find relevant benefits after analysis of video tapes of the patient's gait while using an electrical stimulation orthosis. The social court requested an expert opinion to answer the question as to whether or not there was a relevant functional benefit to using functional electrical stimulation over the existing orthosis or to an alternative treatment. Video documentation was desired by the court. We used the clinic's gait analysis laboratory, which is equipped with a gait course and the claimed video documentation. Standardised video documentation offers substantial advantages for answering forensic questions such as these. It assures reproducibility and comparability of all tested scenarios, with objectification of the individual advantages or limitations. This gain in both validity and reliability fulfills the scientific requirements placed upon an expert assessment.