The Catechism defines grave matter as "violations of what Jesus told to the man who asked him what the most important commandments were, namely, "do not kill", "do not steal", "do not commit adultery", "do not bear false witness", "do not defraud" and "honour your father and your mother".All of these, however, are subject both to the conditions above and to mitigating circumstances (like mental illness, emotional or behavioral disturbance, insanity, retardation, young age, affective immaturity, or developmental disorders) of the individual situation. The Church itself does not provide a precise list of sins, subdivided into the mortal and venial categories. Rather, it is generally considered a matter for a well-formed conscience to decide after a comprehensive, prayer-filled, deliberate examination of conscience. These sins must be specifically confessed and named, giving details about the context of each sin: what sin, why, against what or whom, the number and type of occurrences, and any other factors that may exacerbate or lessen one's responsibility and culpability. It also should not be said that certain of these mortal sins, like purposely missing Mass on Sunday is considered equal in gravity to more grave ones, like first-degree murder: Roman Catholic belief holds that mortal sins can vary somewhat in their seriousness, and thus canon law only criminalizes some of the more serious mortal sins. However, for any sins that lack the above mitigating factors and meet the three criteria listed, the "mortal" effect remains present.
This punishment effect is not the same as that resulting from excommunication or penalties like it, which result when a Roman Catholic commits certain mortal sins that are so serious that the church through law has made them crimes, like abortion or heresy. Because commission of these offenses are so serious, the church forbids the excommunicated from receiving any sacrament (not just the Eucharist) and also severely restricts the person's participation in other church liturgical acts and offices. However, even if excommunicated, a Roman Catholic who has not been juridically absolved is still, due to the irrevocable nature of baptism, a member of the church in the sense that they are still considered members of the "church" that is Christ's human family, another more universal interpretation of the word "Catholic."
Some of these crimes are so serious that they merit not imposed, but automatic, excommunication from the Roman Catholic Church. For this or any related formal penalty to be imposed, one must be aware not only of the seriousness of the offense as a mortal sin, but also of the penalty that is incurred, though this is sometimes more apparent in certain contexts.
Mortal sins are not to be confused with the deadly sins. The latter are not sins but rather categories of sin or vice, corresponding to weaknesses in human nature. Mortal sins may also be called "grave", "grievous" or "serious" sins.
The Roman Catholic teaching on mortal sin was called into question by some within the Church in the late 20th century after the Second Vatican Council. In response to these doubts, Pope John Paul II reaffirmed the basic teaching in his encyclical Veritatis Splendor. It is maintained in the current Catechism of the Catholic Church, which says in section 1035, "Immediately after death the souls of those who die in a state of mortal sin descend into hell."
The Eastern Catholic Churches, which derive their theology and spirituality from same sources as the Eastern Orthodox and Oriental Orthodox, do not use the Latin Catholic distinction between mortal and venial sin, though insofar as it is the doctrine of the Church they hold it. Like the Eastern and Oriental Orthodox, the Eastern Catholic Churches do make a distinction between sins that are serious enough to bar one from receiving Communion (and must be confessed before receiving once again) and those which are not sufficiently serious to do so.
This list is not intended to replace or add to the definition of mortal sin. The list was created with the intent of reminding Catholics of the social nature of many sins, or specifically, how seemingly small offenses (such as pollution) hurt other humans, making the acts sinful. For example, greed has long been considered a cardinal vice, so "inflicting poverty" by extension has always been sinful. "Inflicting poverty" and "accumulating excessive wealth" are not new sins, but manifestations of the sin of greed. Including specific offenses in the list aims to make Catholics aware of the severity of the offense.