The Abbot of Mortemer has been identified as Guillaume Theroude, who took part in the Council of Constance and undertook various missions for Jean, Duke of Burgundy, and was recommended to Henry V by Philip the Good in 1421 as a "bon preudomme, solempnel maistre en theologie."

We encounter him at Rouen in 1423 where he celebrated mass at Saint Cande le Vieux; in 1424 he went to Vernon to seek out Bedford on the behalf of Cardinal de la RochetaiIIé.

According to Denifle and Chatelain, however, the Abbot of Mortemer concerned in the Trial was Nicolas, a monk of Rosières near Salins, de Roseriis, otherwise called Haumont, of the Cistercian order. He was bachelor of theology in 1426 at the same time as Guillaume Evrard and Jean du Quesnay, and prepared for his licentiate with Thomas de Courcelles and Jean Le Fèvre.

He became a licentiate in December 31, 1429, along with Evrard, du Quesnay and Jean Le Sauvage. Proclaimed master at Paris on February 20, 1431, he taught there with so many others of Jeanne's judges (September 1431-1434).

A register of Martin V tells us that he was named Abbot of Mortemer on November 26, 1428. This theologian first took refuge in the opinion of the masters of Paris, and then he judged as did Gilles de Duremort.

He was present at the abjuration.