The interface between medicine and the law is an area which demands further investigation. There can be no criminal capability for an act unless the perpetrator had both the will to so act and the capacity to differentiate and choose whether or not to conform the particular behaviour to that dictated by the law. The capacity for choice must remain the fundamental issue. The range of conditions which can raise volition as a defence include: Somnambulism; post-traumatic syndromes; epilepsy; arteriosclerosis; or acts secondary to cerebral neoplasia. There is need to differentiate between reflex actions and automatisms and it is imperative that terms such as automatism or automatic behaviour are not perverted to allow an excuse for that which is inexcusable. Cases such as that of Cogdon, who was acquitted of murdering her daughter; Ramsbottom who was found guilty of causing a traffic accident despite having a stroke; Dennison in which a driver was found guilty despite epilepsy or Jenkins where the driver was initially found innocent of dangerous driving because of the unpredictable nature of diabetes are discussed. Special attention will be focused upon the case of Sullivan, a landmark in consideration of automatism in epilepsy. The paper examines insane verses non-insane automatism and the Australian legal system as it affects modern neurological practice. Suggestions are proffered as to how the law should be modified to better reflect justice as required within the context of modern medical knowledge. 'The social and psychological pressures that shape our criminals also shape-those who make and remake the laws which aim to control, punish or rehabilitate them, and those who try to change their behaviour.'