This is the most common type of nullity dealt with by the Tribunal. It requires a "judicial" procedure. This basically means that it is decided by judges in accordance with the applicable law of the Church. What is on trial is the validity of the bond of marriage. The participation of both parties is the best way for the judges to reach a just decision. If it can be legally proven that no true consent was given by one or both parties, then a declaration of the invalidity of the marriage will ensue. Since marriage enjoys the favour of the law, the presumption of the validity of the marriage stands until the contrary is proven through the judicial procedure. The "burden of proof" is on the party challenging the validity of the marriage. It is not the Tribunal's responsibility to prove or disprove anything, but only to pass judgment upon the evidence produced by the party challenging the validity. Not any reason for seeking a nullity can be admitted but only those reasons which the law itself permits. These reasons are known as "grounds of nullity." It is not necessary for a party, in a petition for nullity, to express the ground or grounds of nullity in technical legal terms. When the Judicial Vicar reads the petition, he will be able to tell whether a legally permitted ground of nullity is present, could turn out to be present or is clearly absent.

Here are the grounds of nullity due to deficient consent [the legal norm, from the 1983 Code of Canon Law, is in bold type and a simple explanation beneath it in italics):

Canon 1095 - The following are incapable of contracting marriage:

1° those who lack sufficient use of reason;

(You or your spouse did not know what was happening during the marriage ceremony because of insanity, mental illness, or a lack of consciousness caused by such things as drunkenness or substance abuse.)

2° those who suffer from a grave lack of discretionary judgment concerning the essential matrimonial rights and obligations to be mutually given and received;

(A party was affected by some severe psychological problem, whether permanent or transient, which deprived him/her at the time of consent of the mental capacity to grasp realistically and proportionately what was involved in marriage.)

3° those who, because of causes of a psychological nature, are unable to assume the essential obligations of marriage.

(A party, at the time of consent, was unable to fulfill the obligations of marriage because of a serious psychological disorder. He/she may have known realistically what was involved but, when it came to it, he/she was not able to sustain the actions inherent in even just one of the essential obligations of marriage, i.e. permanence until death, marital fidelity, the ordering of the marriage to the good of both spouses and the ordering of the marriage to the gift of new life.)

Canon 1096 §1 - For matrimonial consent to exist, it is necessary that the contracting parties be at least not ignorant of the fact that marriage is a permanent partnership between a man and a woman, ordered to the procreation of children through some form of sexual cooperation.

(A party simply did not know about one or more of the mentioned elements of marriage: e.g. a spouse never actually had the information in his head that marriage was for life.)

§2 This ignorance is not presumed after puberty.

(The human body is of itself ready for marriage after puberty. The presumption is that the human mind is also equipped by then to grasp the basics of marriage. This grasp does not have to be articulated in precise technical words; it can be an intuitive grasp.)

Canon 1097 - §1 Error about a person renders a marriage invalid.

(A party intended to marry a specific individual who was not the individual with whom marriage was celebrated. This ground is rare today.)

§2 Error about a quality of the person, even though it be the reason for the contract, does not render a marriage invalid unless this quality is directly and principally intended.

(A party intended to marry someone who either possessed or did not possess a certain quality, e.g., social status, marital status, education, religious conviction, freedom from disease, or arrest record. That quality must have been directly and principally intended, even more than the person to whom the party was getting married. For example, a man principally and directly intends to marry a beauty queen. This is more important to him than who the person of the beauty queen is. Although this is hardly an exemplary motive for marrying, the marriage is invalid if he marries her erroneously thinking she is a beauty queen when, in fact, she is not.)

Canon 1098 - A person contracts invalidly who enters marriage inveigled by deceit, perpetrated in order to secure consent, concerning some quality of the other party, which of its very nature can seriously disrupt the partnership of conjugal life.

(Before and at the time of consent, a party was intentionally and effectively deceived about the presence or absence of a quality in the other. The one deceiving can have been the other party to the marriage or a third party. The purpose of the deception was to obtain a party’s consent to marriage. The reason for the deception must, however, be sufficiently serious as to "disrupt" married life. In this ground of nullity, it is not the act of consent of the deceiving party which is invalid, but the consent of the party who has been deceived and thus emits consent after having been deliberately induced into error.)

Canon 1099 - Provided it does not determine the will, error concerning the unity or the indissolubility or the sacramental dignity of marriage does not vitiate matrimonial consent.

(A person can have erroneous views about marriage: e.g. I don’t have to be faithful or I don’t have to stay in the marriage until death. This ground of nullity means that only if someone actually chooses to marry because he/she did not have to be faithful, or because he/she believed in divorce, can the marriage be considered as null. In other words, if the error about marriage is the reason why someone chooses to marry, it is null.)

Canon 1100 - Knowledge of or opinion about the nullity of a marriage does not necessarily exclude matrimonial consent.

(A person can enter into a marriage knowing, for example, that there is an impediment to that marriage which has not been dispensed from. The fact that the person knows this does not autoamtically mean that the same person’s consent to marry is either deficient or inexistent.)

Canon 1101 §1 - The internal consent of the mind is presumed to conform to the words or the signs used in the celebration of a marriage.

(This is a principle of human nature, i.e. any party to a marriage intends, or means, what he/she says at the marriage ceremony. The law makes the presumption that this is the case until and unless the presumption falls in the face of evidence which can prove the contrary.)

§2 If, however, either or both of the parties should by a positive act of the will exclude marriage itself or any essential element of marriage or any essential property, such a party contracts invalidly.

(This ground refers to a party who consciously and deliberately, or "positively", excludes something essential to marriage as marriage is intended by the Creator and taught by the the Catholic Church. People can exclude the bond of marriage itself when, for example, the ceremony was observed solely as a means to obtaining something totally extrinsic to marriage itself, e.g., to secure legal status in the country or for money. Or, people can exclude an essential element of marriage such as permanence until death or fidelity to one’s spouse. The law does not use the term, but the exclusion of something essential is also known as "simulation.")

Canon 1102 §1 - Marriage cannot be validly contracted subject to a condition concerning the future.

(A party attached a future condition to his/her marital consent, e.g., I marry you because you will complete your education or your income will be at a certain level or you will become an MP.)

§2 Marriage entered into subject to a condition concerning the past or the present is valid or not, depending on whether or not whatever is subject to condition exists or not.

(Past Condition: the marriage is invalid if that condition did not exist - e.g., I will marry you provided that you have never been married before; I will marry you provided that you have graduated from university. Present Condition: the marriage is invalid if that condition does not exist - e.g., I will marry you provided you don’t have any debt.)

§3 However, a condition as mentioned in §2 may not lawfully be attached except with the written permission of the local Ordinary.

(This norm of episcopal oversight is intended to reduce to a minimum the attachment of any condition whatsoever to marital consent.)

Canon 1103 - A marriage is invalid which was entered into by reason of force or of grave fear imposed from outside, even if not purposely, from which the person has no escape other than by choosing marriage.

(Force: A party married because of an external physical or moral force, whether intentional or not, that he/she could not resist. Fear: A party chose to marry because of fear that was grave, proportionate and inescapable and was caused, whether deliberately or not, by an outside source.)