Our shared enthusiasm for neurosciences as applied to law (“neurolaw”) stems from an age-old alliance between law and science. It promises to shed light on aspects hitherto unexplored about our neuronal functioning and brain structures. Given the importance of tthe issues at stake that have to be decided on a daily basis by criminal courts across Canada, it begs the question as to the possible contributions of neurosciences to Canadian criminal law. Our review of predominantly Canadian caselaw and of both legal and neuroscientific literature has made it possible to determine that these contributions are to be found at two levels: in the determination of the facts between the parties, on the one hand, and in the emergence of new constitutional norms sculpting the contours of our modern criminal law. In determining the facts between the parties to the dispute (interpartes), neuroscientific evidence does not carry a greater probative value than other expertises, of a psychiatric or psychosocial nature, in the absence of corroboration from other expertises, the accused’s psychiatric history or even lay witnesses. Depending on whether the issue in dspute relates more closely to the mental state of the parties, neuroscience is of increased relevance and usefulness. When the issue to be decided involves more than the determination of mental states (e.g. sentencing), the social and personal consequences of neuroscientific results are more closely scrutinized against the applicable legal criteria (e.g. public safety, rehabilitation). All in all, when it comes to determining relevant facts inter partes, neurosciences have up until now less revolutionized our law than being subsumed by it. On the other hand, recent neuroscientific advances have indeed been called upon by the courts – together with other expertises – in the erga omnes constitutional reshaping of the purpose of our modern criminal law. In this regard we identified three main areas of judicial control, namely, the infliction of cruel and unusual punishment on adolescent offenders, the capacity of consenting, and decriminalization of psychoactive substances. The prediction of offenders’ recidivism from neurological markers is also beginning to be more seriously studied.

Keywords : neurosciences, criminal law, criminal responsibility, sentencing, mental state / disorder