VATICAN CITY — When a Vatican court convicted a Chilean predator priest of sex crimes, it went out of its way to affirm the credibility of his victims. Their testimony had been consistent and corroborated, while their motives in coming forward had been only to “free themselves of a weight that had tormented their consciences,” the tribunal said.

One key witness in the Rev. Fernando Karadima’s 2010 trial is preparing to testify again, this time in a spinoff case with potentially more significant consequences. Juan Carlos Cruz’s allegations of a cover-up raise questions about Pope Francis’ already shaky track record on preventing clergy sex abuse and concealment.

Cruz has accused Chilean Bishop Juan Barros of having been present when Karadima kissed and fondled him as a 17-year-old, and of then ignoring the abuse. One of Francis’ top advisers has privately called Cruz a liar who is out to destroy the Chilean church. Francis, who has called allegations against Barros slander, may have accepted the adviser’s take.

After his defense of Barros sparked an outcry during his recent trip to Chile, Francis did an about-face and asked Maltese Archbishop Charles Scicluna, a former Vatican sex crimes investigator, to gather testimony about Barros and then report back. Cruz, who now works in communications in the U.S., is his first witness Saturday.