This article provides a discussion about criminal insanity regulation in Norway, Sweden and the Netherlands, with a focus on the roles of legislators, judges and experts in the concretisation of the legal meaning of criminal insanity. The authors recognise that these three countries reflect different ideal type rule constructions that are interesting to study comparatively. The article addresses the following overall questions: To what extent and in what way do the different rule constructions also involve different views on the roles of legislators, judges and experts? And in case of competing models, which is the better solution? [---]