After coming under excoriating public criticism, Pope Francis has decided to send the Vatican's most respected sex crimes expert to Chile to investigate a bishop accused by victims of covering up for the country's most notorious pedophile priest.

The Vatican said Tuesday that Maltese Archbishop Charles Scicluna would travel to Chile "to listen to those who have expressed the desire to provide elements" about the case of Bishop Juan Barros.

Police detain a protester dressed as a priest as Pope Francis arrives in Santiago, Chile on Jan. 15. (Carlos Vera/Reuters)

The move marks the first known time the Vatican has launched a full-blown investigation into allegations of sex abuse coverup. It comes after Francis was harshly criticized for his defence of Barros by the media, survivors of abuse, his fellow Jesuits and by some of his most trusted advisers.

The Barros controversy

The controversy surrounding Barros dominated Francis' just-ended trip to Chile and Peru and exposed his blind spot about clerical abuse. Even the head of his abuse advisory panel, Cardinal Sean O'Malley of Boston, publicly rebuked him for his dismissive treatment of victims and tried to set him straight.

Barros was a protege of the Rev. Fernando Karadima, a charismatic and politically powerful priest who was sanctioned by the Vatican for sexually abusing minors in 2011. His victims testified to Chilean prosecutors that Barros and other priests in the El Bosque community saw Karadima kissing youngsters and were aware of his perversions, but did nothing.

After Karadima was sanctioned by a church court, Chile's bishops were so intent on trying to stem the fallout from the scandal that they persuaded the Vatican to have Barros and two other Karadima-trained bishops resign and take a yearlong sabbatical, according to a 2015 letter obtained by The Associated Press.

But Francis stepped in and put a stop to the plan, arguing that there wasn't any proof against them. He overruled the Chilean bishops' objections and in January 2015 appointed Barros to head the diocese of Osorno.

'I am convinced he is innocent'

The issue haunted Francis' recent trip, and imploded after he told a Chilean journalist on Jan. 18 that the accusations against Barros were slander and he demanded "proof" against Barros to believe them. After O'Malley rebuked him, Francis apologized for having demanded proof, but he stood by his belief that the accusations against Barros were "calumny."

"I am convinced he is innocent," Francis declared during an in-flight press conference while returning home from Peru on Jan. 21.

Francis seemed unaware that Karadima's victims had placed Barros at the scene and were the original source of the accusations against him. Barros twice offered his resignation, but Francis twice rejected it.

Barros said Tuesday that he welcomed "with faith and joy" the Pope's decision to have Scicluna investigate and prayed that the process would uncover the truth, according to a statement read by the spokesman of the Chilean bishops' conference.

'As if I could have taken a selfie or a photo while Karadima abused me'

In the days after the Pope's comments, Karadima victim Juan Carlos Cruz pointedly told Francis that he couldn't offer the "proof" the Pope demanded.

"As if I could have taken a selfie or a photo while Karadima abused me and others and Juan Barros stood by watching it all," Cruz tweeted on Jan. 19.

In this 2015 photo, Juan Carlos Cruz poses for a portrait. Cruz, now a 51-year-old journalist, recalls that he and another teen boy were molested by Rev. Fernando Karadima, all while the Rev. Juan Barros watched. (Matt Rourke/Associated Press) After Francis insisted he had never received any testimony from victims but would welcome it, Cruz told The Associated Press: "If he wanted evidence, why didn't he reach out to us when we were willing to reaffirm the testimony that not only us, but so many witnesses, have been providing for more than 15 years?"

Scicluna is going to Chile precisely to do that. Vatican spokesman Greg Burke said Scicluna would travel to Santiago "as soon as possible," but he noted that the case requires preparation and thoroughness.

Scicluna was the Vatican's long-time sex crimes prosecutor in the Congregation for the Doctrine of the Faith, and was instrumental in finally bringing to justice the 20th century Catholic Church's most notorious pedophile, the Rev. Marcial Maciel, founder of the Legion of Christ.

Scicluna, currently archbishop of Valletta and head of a sex abuse appeals tribunal at the Vatican, is now something of a hero to survivors of sex abuse for having finally understood the dynamic of the clerical abuse scandal and for having vigorously prosecuted Maciel over the objections of the Vatican's then-secretary of state.

New phase in dealing with sex abuse

The decision to send Scicluna in to investigate allegations of a cover-up marks a new phase in the Vatican's decades-long effort to come to terms with clergy abuse, and it could fuel demands for the Vatican to more actively investigate and sanction religious superiors who turn a blind eye to priests who rape, sodomize and molest children.

While thousands of abusive priests have been defrocked over the years, only a handful of bishops are known to have been removed because they mishandled reported cases by moving abusers around rather than sanctioning them.

Francis vowed to hold such bishops accountable, but he scrapped a proposed Vatican tribunal to discipline negligent bishops after Vatican canon lawyers objected. Instead, he said such cases would be investigated by existing Vatican offices, but the process lacks any transparency.