A frequent mistake, underlined by Stephen Morse is to assume that if a behaviour is caused and explained, it is also legally excused. Our actions always have causes. Scientific knowledge of these causes is progressing, and the technical means available to assess causes are improving,and contributing to explaining our actions. But an explanation is neither a justification nor an excuse . The causal link is not in itself a legal reason for excusing, nor is it an extenuating circumstance.