The most common serious crime was murder, which accounted for 55 to 80 percent of the major crimes described in court archives. It was largely the result of the strict code of honor in effect in the Middle Ages; an insult, such as throwing a person's hat in the mud, required a response, which often led to a death. A man whose wife committed adultery was considered justified if he killed the other man. In many cases, these types of murders resulted in a royal pardon.^[45] Petty crime was common; men did not have pockets in their clothing, but instead carried purses around their necks or on their belts. Thieves cut them loose and ran away.

Heresy and sorcery were considered especially serious crimes; witches and heretics were usually burned, and the king sometimes attended the executions to display his role as defender of the Christian faith. Others were decapitated or hanged. Beginning in about 1314, a large gibet was built on a hill outside of Paris, near the modern Parc des Buttes Chaumont, where the bodies of executed criminals were displayed.

The city's main prison, courts and residence of the Provost of Paris were located in the Grand Châtelet fortress, shown here as it appeared in 1800

Prostitution was a separate category of crime. Prostitutes were numerous and mostly came from the countryside or provincial towns; their profession was strictly regulated, but tolerated. In 1256, the government of Louis IX tried to limit the work areas of prostitutes to certain streets, including the Rue Saint-Denis and Rue Chapon on the Right Bank and the Rue Glatigny on the Île de la Cité, but the rules were difficult to enforce. Prostitutes could be found in taverns, cemeteries, and even in cloisters. Prostitutes were forbidden to wear furs, silks, or jewelry, but regulation was impossible, and their numbers continued to increase.^[46]

The Church had its own system of justice for the ten percent of the Paris population who were clerics, including all the students of the University of Paris. Most clerical offenses were minor, ranging from marriage to deviations from official theology. The Bishop had his own pillory on the square in front of Notre Dame, where clerics who had committed crimes could be put on display. For more serious crimes, the Bishop had a prison in a tower adjoining his residence next to the Cathedral, as well as several other prisons for conducting investigations in which torture was permitted. The church courts could condemn clerics to corporal punishment or banishment. In the most extreme cases, such as sorcery or heresy, the Bishop could pass the case to the Provost and civil justice system, which could burn or hang those convicted. This was the process used in the case of the leaders of the Knights Templar. The Abbeys of Saint-Germain-des-Prés and Sainte-Geneviève were largely responsible for justice on the Left Bank and had their own pillories and small prisons.^[47]

Royal justice was administered by the Provost of Paris, who had his office and his own prison in the Grand Châtelet fortress on the Right Bank at the end of the Pont de la Cité. He and his two examiners were responsible for judging crimes ranging from theft to murder and sorcery. Royal prisons existed in the city; about a third of their prisoners were debtors who could not pay their debts. Wealthier prisoners paid for the own meals and bed, and their conditions were reasonably comfortable. Prisoners were often released and banished, which saved the royal treasury money. Higher crimes, particularly political crimes, were judged by the Parlement de Paris, which was composed of nobles. The death sentence was very rarely given in Paris courts, only four times between 1380 and 1410. Most prisoners were punished with banishment from the city. Beginning in the reign of Philip VI, political executions, while rare, became more frequent; In 1346 a merchant from Compiègne was tried for saying that Edward III of England had a better claim to the French throne than Philip VI; he was taken to the market square of Les Halles and chopped into small pieces in front of a large crowd.^[48]

"Kyrie eleison" (which appears many times), is from the opening of the ordinary of the Mass (the parts that are said at most every Mass, regardless of the church calendar).  It's actually Greek, not Latin, and it means "Lord, have mercy".

The "Dies irae" (which also appears a few times) comes from the Requiem Mass (the Mass for the Dead), and in this section speaks of Judgment Day.

In "Hellfire" the priests are singing part of the "Confiteor" (which, in modern times, is not sung, but spoken) which is a communal confession of sins.  From it comes the phrase "mea culpa" which is sometimes used in written/spoken English, and means "my fault".