In Church tradition, a person who is seen as exceptionally holy can be declared a saint by a formal process, called canonization. Formal canonization is a lengthy procedure often taking many years, even centuries, but this is all depending on the story and circumstances of the person(s).
There are several steps to the canonization process. This first phase of canonization begins on a diocesan level, with the bishop of the diocese in which the person died as the responsible liaison for beginning the investigation. Five years must pass from the time of a candidate’s death before a cause may begin. This is to allow greater balance and objectivity in evaluating the case and to let the emotions of the moment dissipate. However, the pope can dispense from this waiting period (as was done by Pope Benedict XVI in the cause for his predecessor, Saint John Paul II).
The diocese, parish, religious congregation, or association asking for a cause to be opened, known as the petitioner, asks the bishop through a person known as thepostulator to open the investigation. (A bishop also may begin a cause on his own initiative.) The bishop applies to Rome seeking a nihil obsat – a Latin term meaning “no obstacles found” (against the petition). Once the “nihil obstat‟ of the Holy See is obtained, he forms a diocesan tribunal for this purpose. At this stage, the person investigated is given the first official title for canonization called “Servant of God.”
Witnesses are crucial for the cause of a saint. Thus the witnesses are called before the tribunal to recount concrete facts on the exercise of Christian virtues considered heroic, that is, the theological virtues of faith, hope and charity, and the cardinal virtues of prudence, justice, temperance and fortitude, and others specific to his or her state in life. In addition, all documents written by and about the candidate must be gathered and examined.
The bishop also will consult with the national bishops’ conference, or at least the bishops of his region to solicit their opinions on the merit and timeliness of introducing the cause. Likewise, he will consult the general public, asking for anyone with any knowledge of the candidate to come forward. These experts known as procurators spend much time in the files of the named. After this, the report on the candidate is given to the bishop of the area and more studying is done. It is then sent to the dicastery (department) in the Roman Curia Offices known as the Congregation for the Causes of Saints.
At some point, permission is then granted for the body of the Servant of God to be exhumed and examined. A certification ("non cultus") is made that no superstitious or heretical worship or improper cult has grown up around the servant or his or her tomb, and relics are taken.
If the application is approved, the person may be granted the proclaimed title by the Pope of "Venerable.” The Servant of God now has proven to have exhibited the theological virtues of faith, hope and charity, and the cardinal virtues of prudence, justice, fortitude and temperance, to a heroic degree. This is the next official step toward canonization.
A Venerable has as yet no feast day, no churches may be built in his or her honor, and the church has made no statement on the person's probable or certain presence in heaven, but prayer cards and other materials may be printed to encourage the faithful to pray for a miracle wrought by his or her intercession as a sign of God's will that the person be canonized.
Further investigations may lead to the candidate's beatification when the person is and given the title of "Blessed.” At a minimum, two important miracles are required to be formally declared a saint. Such miracles arrive when a prayer request from an individual seeks the intercession of the saintly candidate. The request must be shown to be that of a cure or a phenomena beyond the explanation of science, medicine or tradition. These miracles must occur after the death of the person. The first one must occur after the person has been recognized as 'Venerable' and then again after he or she is declared 'Blessed.'
The next step is called beatification. For the beatification of a Servant of God, a miracle attributed to his/her intercession, verified after his death, is necessary. The required miracle must be proven through the appropriate canonical investigation, following a procedure analogous to that for heroic virtues. This investigation too is concluded with the appropriate decree. Once the two decrees are promulgated (regarding the heroic virtues or martyrdom and the miracle) the Holy Father decides on beatification, which is the concession of limited public veneration – usually only in the diocese, region, or religious community in which the Servant of God lived. With beatification the candidate receives the titled of “Blessed.”
Beatification is a statement by the church that it is "worthy of belief" that the person is in heaven, having come to salvation. This step depends on whether the Venerable is a martyr or a "confessor". A martyr meaning that he/she died for the Catholic Faith; a confessor meaning that he/she bore witness to a holy and exemplary life.
For canonization, the final step, another miracle is needed, attributed to the intercession of the one who is already recognized and declared Blessed and having occurred after his/her beatification. The methods for affirming the miracle are the same as those followed for beatification. Canonization is understood as the concession and requirement of public veneration in the Universal Church. With canonization, the Blessed acquires the title of “Saint.”
The saint is assigned a feast day which may be celebrated anywhere within the Catholic Church, although it may or may not appear on the general calendar or local calendars as an obligatory feast, parish churches may be built in his or her honor, and the faithful may freely and without restriction celebrate and honor the saint.
Although a recognition of sainthood by the Pope does not directly concern a fact of divine revelation, it must still be "definitively held" by the faithful as infallible under (at the very least) the Universal Magisterium of the Church since it is a truth connected to revelation by historical necessity.