A Defect (or Lack) of Form case, also called an Absence of Canonical Form case, is an administrative process that is used when Catholics have a wedding outside the Catholic Church. This is technically called a declaration of nullity (an annulment) based upon a defect/lack or absence of canonical form, acknowledging that the parties did not exchange matrimonial consent before a Catholic priest (or deacon) and two witnesses in a Catholic church as is required by Canon 1108 §1 of the Code of Canon Law. When Catholics fail to observe this law, the marriage is invalid. These cases, where Catholics do not have a wedding according to canonical form, account for more than half of all the annulments granted in the Catholic Church.
A lack of canonical form case can only come into play if one of the parties to the marriage is a Catholic (who did not leave the Catholic Church by a formal act between 1983 and 2009). In a case involving a lack of canonical form due to a wedding taking place “outside” the Catholic Church, the Tribunal must be able to establish certain facts including the following: that the Catholic party was bound by canonical form; that the Catholic party had not left the Catholic Church by a formal act prior to or at the time of the wedding; and that the marriage was never subsequently celebrated in the Catholic Church (via “convalidation”) or otherwise rendered valid (i.e., sanatio-in-radice) in the eyes of the Catholic Church.
Thus, for example, in a case where a Catholic would simply contract marriage by a Justice of the Peace or other civil official, or before a non-Catholic minister, the marriage would be considered invalid due to lack of proper canonical form. A “defect,” in the strict sense, in the celebration of the canonical form of marriage might occur if the priest or deacon officiating at the wedding failed to request and receive delegation when necessary.