Episcopal courts adjudicate in proceedings for declaring a marriage void and in these cases psychiatrists and psychologists are appointed as experts. Expert judgment requires the expert to follow a specific substantive approach when preparing the expertise, as well as knowledge of canon legal provisions. Canon law makes validity of a relationship dependent on fulfilment of premises of a valid marriage at the time of the marriage, thus accepting the possibility of an invalid marriage. The so-called consensual and indirectly mental incapacity to marry is dealt with in canon 1,095, which says that the following are incapable of contracting marriage: (1) those who lack the sufficient use of reason; (2) those who suffer from a grave defect of discretion of judgment concerning the essential matrimonial rights and duties mutually to be handed over and accepted; and (3) those who are not able to assume the essential obligations of marriage for causes of a psychic nature. Episcopal courts use terminology that is not found in psychiatry or clinical psychology. However, specific psychopathological conditions stand behind specific formulations in the Code, and they should be taken into account by experts in their analyzes. In proceedings before common courts, only mental illness and mental retardation are taken into account, and no specific disorders are mentioned in Church legislation, which means that experts must consider a wide range of mental dysfunctions in their assessments.