Psychiatric expertise is necessary to the courts in many legal situations, both in criminal and in civil matters, and is subject to the same rules as any other expertise. However, psychiatry and its object are unique. The relationship between the judge and the psychiatric expert can be affected by many social or professional factors, or by legal or procedural matters.
While jurists speak of this relationship as a usurpation of the role of the judge by the psychiatric expert, psychiatrists believe that, on the contrary, their expertise is completely distorted by the judiciary process. In reality, however, this is not always the case; while psychiatric expertise is, generally speaking, one piece of evidence among many, it can also occupy a central place in the decision-making process.