A pronouncement of death is made in Latin and is certified by a physician. The camerlengo, or chamberlain, then calls out the pontiff's baptismal name -- "Karol" for Pope John Paul II -- three times in a ritual to confirm there is no response. In the past, the camerlengo struck a silver hammer against the pope's forehead to confirm his death, but it's unclear if the ritual is still active.
The camerlengo then destroys the symbols of that papacy: the "Pescatorio," or Ring of the Fisherman, and the dies used to make lead seals for apostolic letters. The pope's quarters are sealed and funeral arrangements are begun by the camerlengo, the most important Vatican official until a new pope is elected. Spanish Cardinal Eduardo Martinez Somalo, 78, has been the camerlengo since 1993. Vatican flags fly at half-staff. According to tradition, the Bronze Door at St. Peter's Basilica is closed.
An official nine-day mourning period, known as the "novemdiales," follows the death of a pope. The tradition dates from ancient Rome and a ceremony held nine days after a death. The pope's body lies in state in St. Peter's Basilica in the Clementine Chapel, which was begun by Michelangelo and completed by Giacomo Della Porta for the Jubilee in 1600. After the death of John Paul I in 1978, an estimated 750,000 mourners filed past the body over three days. Many more could pay homage to John Paul II.
The funeral and burial must be held between the fourth and sixth day after death except for unspecified "special reasons," according to rules established in 1996. Weather permitting, it would be held in St. Peter's Square. Many of the world's leaders and other dignitaries would likely attend. Also on hand would be many of the Cardinals, who select the new pope. During one part of the Mass, the ceremonial Swiss Guards, who wear distinctive purple-gold-and-red uniforms, kneel and dip their halberds with their right hand and salute with their left.
Most popes in recent centuries have chosen to be buried beneath St. Peter's Basilica. After the funeral, their lead-lined coffins -- which can weigh close to a half ton -- were carried through the "door of death" on the left side of the main altar in the basilica. A single bell tolled. The coffin was lowered into a marble sarcophagus and covered by a huge stone slab. The Vatican has not clarified whether Pope John Paul II seeks such a burial. There is speculation that the Polish-born pontiff could choose to be interred in Krakow's Wavel Cathedral alongside Polish royalty.
At least 15 days (and no more than 20 days) following the death of the pope, the church's cardinals gather in Rome for a conclave to elect a new pope. Unless circumstances prevent it, the conclave takes place in the Vatican palace, where the cardinals gather and vote in the Sistine Chapel. Officially, the cardinals are forbidden to discuss possible papal successors before the death of a pope, although private conversations do occur.
Once in Rome, the cardinals stay at the Casa di Santa Marta in the Vatican Grounds, located several hundred yards from St. Peter's Basilica. John Paul II's Universi Dominici Gregis ("Of the Lord's Whole Flock") provided for such modern accommodations -- a far cry from the spartan rooms in the Papal Palace issued to the cardinals in earlier conclaves.
Secrecy is of utmost importance during the conclave. No cardinal may leave without consent, and all the telephones are disconnected and the TV sets taken away. Radios, recording devices, newspapers and cameras are all forbidden, and no letters or documents are allowed in or out unless they are inspected by both the secretary of the conclave and a commission charged with guarding its integrity. The cardinals take an oath to observe the rules laid down by "Romano Pontifici Eligendo," which enjoin secrecy and forbid the electoral interference by civil authorities. The church holds these rules of secrecy in the highest regard: The penalty for disclosing anything about the conclave that must be kept secret is automatic excommunication.
Contrary to what many people think, there are surprisingly few qualifications for someone to become pope: The cardinals can elect any baptized male to the papacy. Actually, even the requirement of baptism is negotiable -- although once a man accepts election to the papacy, he must be willing to be baptized, ordained a priest and consecrated bishop of Rome (and meet the qualifications of those positions). In recent centuries, however, church practice has been to elect someone from among the College of Cardinals.
Only cardinals under the age of 80 are eligible to vote, and only voting cardinals are allowed into the Sistine Chapel for the election. The first vote is taken in the afternoon of the first day of the conclave. In the following days, they will vote twice each morning and once each afternoon until a pope is selected. If no one is elected within the first nine votes, then they may devote up to a day for prayer and discussion before resuming. They may do the same every seven unsuccessful votes after that.
In order to be elected, a candidate must receive two-thirds of the vote. However, in accordance with a change to papal electoral policy initiated by John Paul II in 1996, if the College of Cardinals is deadlocked after upwards of 12 or 13 days, they can decide to alter the voting process to allow for election by an absolute majority -- 50 percent plus one. The rule change also stipulated that the only method of electing the pope is by scrutiny, i.e., silent ballot -- thus excluding election by acclamation (which almost never happens) and by committee (a technique sometimes used to settle deadlocks).
The actual process of voting is quite elaborate. One at a time, in order of precedence, the cardinals approach the altar while holding up their folded ballots -- rectangular cards with the words "Eligo in Summum Pontificem" ("I elect as supreme pontiff") printed at the top. The elector kneels in prayer before the altar for a short while, before rising. He says, "I call to witness Christ the Lord who will be my judge, that my vote is given to the one who before God I consider should be elected," and places his ballot on a thin, flat plat called a paten. Then he uses the paten to drop the ballot into a chalice.
After everyone has voted, scrutineers count the ballots before they are unfolded. If the number of ballots does not match the number of electors, the ballots are burned without being counted and another vote is immediately taken. If the number of cards does match the number of electors, the scrutineers, who sit at a table in front of the altar, begin counting the votes. The first scrutineer unfolds the card, notes the name on a piece of paper and passes the card to the second scrutineer. He then notes the name and passes it to the third scrutineer, who reads it aloud. The last scrutineer uses a threaded needle to pierce each card through the word "eligo." After all the ballots have been counted, the ends of the thread are tied and the joined cards are placed in an empty receptacle. Then the scrutineers add up totals votes for each candidate.
After the vote, the secretary of the conclave and the master of ceremonies burn the ballots, adding special chemicals to make the smoke appear white or black to those waiting in St. Peter's Square. Black smoke signifies that no one received enough votes to be elected pontiff, while white smoke signifies the election of a new pope.
After the winner of the papal election is announced, the dean of the College of Cardinals asks the pope-elect, "Do you accept your canonical election as supreme pontiff?" After the prospective pope accepts, the dean asks him what name he would like to go by. Assuming he is already a bishop, he immediately becomes the new pope. The Dean of the College of Cardinals then steps onto the main balcony of the Vatican and declares: "Habemus Papam." ("We have a Pope.") The new pope then appears and delivers his Apostolic Blessing.
• There is a custom in the history of the College of Cardinals of selecting someone who is very different from the previous pope.
• John Paul II has appointed more cardinals than any other pope.
• There are 117 cardinals under the age of 80, which makes them eligible to vote. John Paul II has selected all but three of those eligible.
• A pope's election cannot be invalidated once he is chosen, even if he bought the election.
• The custom of taking a new name began in 533, when a priest named Mercury was elected pope and felt the name of a pagan god was inappropriate for the successor of St. Peter.
• A few early popes, including St. Peter, may have appointed their own successors.
• In the early church, popes were usually chosen by the clergy and people of Rome in the same way that bishops in other dioceses were elected. This democratic process worked well when the church was small and united, but disagreements led to factions that fought over the papacy.
• After the eighth century, the papal electors were limited to the Roman clergy.
• Pope Leo I (440-61) described the ideal by saying that no one could be a bishop unless he was elected by the clergy, accepted by his people and consecrated by the bishops of his province.
• In an attempt to reform the electoral process, Nicholas II (1059-61) proposed a system whereby the cardinal bishops would meet to nominate a candidate and then invite the cardinal priests to vote on him. In 1179, Alexander III modified this system by including all the cardinals in the election process from the beginning.
• In 1274, Gregory X institutionalized this practice of sequestering the cardinals when he established the conclave. Under his system, the cardinals would be locked in one room, where they would sleep and vote. After three days, their food would be limited to one dish per meal. After eight days, they got only bread and water. Such severe regulations were not always enforced, but conclaves could still be dangerous to a cardinal's health.
• In July 1623, eight cardinals and 40 of their assistants died of malaria during a very hot conclave.
• The last conclave to last more than four days was in 1831. It lasted 54 days.
Fox News' Matt Castellan and Alec Melman contributed to this report.