Canon 1678. §1 In cases of the nullity of marriage, a judicial confession and the declarations of the parties, possibly supported by witnesses to the credibility of the parties, can have the force of full proof, to be evaluated by the judge after he has considered all the indications and supporting factors, unless other elements are present which weaken them.

§2 In the same cases, the testimony of one witness can produce full proof if it concerns a qualified witness making a deposition concerning matters done ex officio, or unless the circumstances of things and persons suggest it.

§3 In cases of impotence or defect of consent because of mental illness or an anomaly of a psychic nature, the judge is to use the services of one or more experts unless it is clear from the circumstances that it would be useless to do so; in other cases the prescript of can. 1574 is to be observed.

§4 Whenever, during the instruction of a case, a very probable doubt arises as to whether the marriage was ever consummated, the tribunal, having heard both parties, can suspend the case of nullity, complete the instruction for a dispensation super rato, and then transmit the acts to the Apostolic See together with a petition for a dispensation from either one or both of the spouses and the votum of the tribunal and the bishop.