VATICAN CITY -- For centuries, the Vatican's canon law system busied itself with banning books and dispensing punishments that included burnings at the stake for heretics.

These days, the Vatican office that eventually replaced the Roman Catholic Inquisition is knee-deep in processing clergy sex abuse cases. The procedures of the Congregation for the Doctrine of the Faith will be on display this week as high-ranking bishops summoned by Pope Francis attend an unprecedented four-day tutorial on preventing sex abuse and prosecuting pedophile priests

Here is a primer on the Catholic Church's regulations for investigating both priests accused of molesting children and superiors who have been accused of covering up those crimes.

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ARE POLICE CALLED IN SUSPECTED SEX ABUSE CASES?

In countries where clergy are required to report child abuse, bishops and superiors of religious orders are supposed to notify police when someone alleges that a priest molested a child and they are supposed to cooperate with any investigations.

However, the policy is nonbinding and only was articulated publicly in 2010 when the Vatican posted it on its website. Prior to that, the Vatican long sought to prevent public law enforcement agencies from learning about abusers in the clergy.

Irish bishops who considered adopting a mandatory reporting policy in 1997 received a letter from the Vatican warning that their in-house church investigations could be compromised if they referred cases to Irish police.

Nowadays, the Vatican justifies not having a binding policy that requires all sex crimes to be reported to police by arguing that accused clergy could be unfairly persecuted in places where Catholics are a threatened minority.

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WHAT'S THE CANONCAL PROCEDURE?

Once a bishop or superior receives an allegation of abuse by one of his priests, he is supposed to conduct a preliminary investigation. If the claim has a "semblance of truth" he sends the case to the Congregation for the Doctrine of the Faith for review.

The superior often will remove the priest from public ministry pending the outcome of the investigation.

The CDF, as the congregation is known, has a staff of 17 canon lawyers who process the cases. There has long been a case backlog, however, and at one point Francis acknowledged it had topped 2,000, with cases taking years to reach a verdict.

Usually, the CDF sends the case back to the bishop to investigate more fully, either through a full canonical trial or via an expedited administrative process. If the evidence is overwhelming and serious, the CDF can send the case straight to the pope to decide the priest's fate.

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WHAT ARE THE PENALTIES FOR SEX ABUSERS?

Penalties can range from the mild — a temporary suspension from publicly celebrating the sacraments or exercising ministry — to the more serious, such as defrocking, which is removing a cleric from the priesthood.

Elderly priest abusers often have been spared defrockings, even for heinous crimes. Instead, they were given a lifetime of "penance and prayer."

Just last week, though, Francis defrocked 88-year-old Theodore McCarrick, the once-prominent American cardinal who was convicted by the Vatican's canon law tribunal of sexually abusing minors and adults.

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HOW MANY PRIESTS HAVE BEEN DEFROCKED FOR SEX ABUSE?

The Vatican told a United Nations committee that 848 priests had been defrocked and another 2,572 given lesser sanctions from 2004-2014.

Since then, the Vatican has not released any more data on defrockings, evidence that such transparency was not universally welcomed in the Holy See.

There is a fierce debate within the Catholic hierarchy about whether priests should be defrocked for sex abuse or given lesser sanctions. Many powerful cardinals close to Francis, aghast at the thinning of clerical ranks from so many defrockings, favor a more "merciful" approach.

Archbishop Charles Scicluna, who enforced a tough line on abusers when he was the Vatican's lead sex crimes prosecutor from 2002-2012, has recently returned to a position of power at the Congregation for the Doctrine of the Faith. He said this week he would support releasing new defrocking statistics.

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WHAT ABOUT ABUSE COVER-UPS?

While the Vatican under Pope Benedict XVI cracked down on abusive priests, the bishops who shielded them largely got a pass.

In 2015, with demands for accountability growing, Francis agreed to create a tribunal section within the Congregation for the Doctrine of the Faith to handle cases accusing bishops of negligence. But a year later, he scrapped the plan.

Instead, the pope outlined procedures to investigate bishops and punish them, making clear they could be removed from office if they were found to have been negligent in handling abuse cases of their clergy.

In addition, the Vatican office that vets new bishops, in soliciting comments about potential candidates, now includes an "explicit question on how the candidate has dealt with sexual abuse issues and whether he has been criticized for not doing the right thing," Scicluna said.

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More AP coverage of clergy sex abuse at https://www.apnews.com/Sexualabusebyclergy