Before performing each marriage, the Catholic parish priest conducted an investigation to ensure that the bride and groom met the church's requirements. Although not extant for all parishes, the written records of these investigations are available in separate books or files from the sacramental registers of marriage in many parishes.
In each marriage investigation, whether conducted by the parish priest prior to the marriage or under the direction of the bishop's vicar general in the investigations for a marital dispensation, an effort was made to ascertain that this marriage was an exercise of free will on the part of the parties. In the case of the parish investigation, a declaration of consent by each party was obtained, stating that the party wanted the marriage of his or her own "spontaneous and free will."
The honor of the Catholic Church as an institution was maintained by being certain that a full investigation was conducted and the parties were free from (that is, they were not in violation of) the impediments imposed by Catholic canon law. Under canon law there were a number of impediments to marriage, many of which could be dispensed with or forgiven by the bishop. Included in these were two major categories: diriment, which even if discovered after marriage voided the union; and preventative, which only stood as obstacles if discovered before marriage. Typical of the latter would be the objection that one of the parties had made a previous promise to marry another person. The following were the diriment impediments as they had developed by the end of the Middle Ages and the Council of Trent: