The current Canadian legislation regarding dangerous offenders is reviewed, with specific emphasis on the role of the required psychiatric testimony. It is suggested that, although this legislation as it is currently formulated could be viewed as an attempt to broaden the insanity defence, and permit the diversion of mentally ill offenders from a punitive to a therapeutic milieu, it enables the preventive detention of recidivist offenders. Some fundamental ethical issues which follow from this are identified, together with the issues which have dominated expert testimony in hearings held in British Columbia during the past 13 years.