During the initial stages of Joan's rehabilitation, in 1452, Bréhal was given the task of reviewing her case by the papal legate in France, Cardinal Guillaume d'Estouteville.

During the course of that year and up until 1453, Bréhal traveled all around the country and he questioned several witnesses in Rouen, where Joan was imprisoned and executed, sought information all over the kingdom about her life, and consulted several lawyers and theologians in both France and Europe, as well as Thomas Basin, bishop of Lisieux.

On November 7, 1455, he presided the retrial at Notre-Dame,[1] where he questioned, along with several theologians and clergymen of all Europe, a total of 115 witnesses that knew Joan; from childhood friends, soldiers whom served under her command, citizens of Orleans and, with not so much enthusiasm, former members of the tribunal that condemned her in 1431.

[2] With all the information he heard, Bréhal declared in June 1456 that Joan had died a martyr and posthumously excommunicated Pierre Cauchon, the main instigator of the trial, branding him as an heretic who was pursuing a secular vendetta.

In Orleans, he presided over the commemorative feasts and it was likely that he met Joan's elderly mother during a celebratory banquet that the citizens offered to Inquisitor Bréhal on July 27.