Mert was a guard at Shawkshank State Penitentiary.
He was friends with Cpt. Byron Hadley, and didn't have a problem with abusing prisoners, shown when he stepped aside to let Hadley throw Andy off a roof without hesitation. When Bogs puts Andy in the hospital, Mert, along with Hadley, beats Bogs nearly to death, resulting in him never walking again. Later on he is seen while Andy does tax returns for him.