The 18th-century Franciscan missionary Junipero Serra is expected to be elevated to sainthood this fall in Washington, D.C.

Serra's impending sainthood has generated protests from Native Americans who say the priest spread disease, wiped out native populations and enslaved converts as he built a Catholic mission system throughout what is now California.

A primer on becoming a saint:

THE ROAD TO SAINTHOOD:

Becoming a saint in the Catholic Church is a long process that can take decades or even centuries.

A candidate must first be recognized as "venerable" by the pope for being a Catholic who lived out heroic virtues.

The person must next attain beatification — the final step before possible sainthood — that requires the Vatican confirm a miracle attributed to the candidate's intercession.

Sainthood — also called canonization — comes last and requires (in most cases) confirmation of a second miracle.

WHO DECIDES

Within the Vatican, the Congregation for the Causes of Saints makes recommendations to the pope on candidates for beatification and canonization.

Martyrs, or those who were killed out of hatred for the faith, don't need a miracle to be beatified though they need one to be canonized. In rare cases, such as Serra's, the pope can also fast-track the candidate to sainthood without the usual second miracle.

These so-called "equipollent" canonizations are rare, but Pope Francis has done several to honor what he's called "great evangelizers."

In his announcement last month, he said Serra fit that category.

A STICKY DECISION

Decisions about who to elevate to sainthood in the Catholic Church are often political and can sometimes be held up for decades or centuries.

Many people were opposed to sainthood for St. John Paul II, for example, because of his mishandling of the sex abuse scandal.

Jewish opposition to Pope Pius XII has held up his beatification — the last step before possible sainthood — for decades.

It's extremely rare for a beautification or canonization to be canceled after it's been publicized, however.

In one of the only such cases in recent times, a newly elected Pope Benedict XVI suspended the planned beatification of a French priest in 2005 so the Vatican could investigate allegations of anti-Semitism in his writings.

The process for canonizing that priest, the Rev. Leon Dehon, had begun more than 40 years earlier.