Aron was arraigned Thursday in Brooklyn. An attorney spoke for the suspect.
Aron is charged with murdering Leiby after the boy became lost while walking home from camp for the first time and asked for directions, then got into his car.
Kletzky's death sparked wide-spread grief and heated debate within the Chasidic community. A charity created in his name by the Kletzky family has raised $265,399.
A psychological exam requested by defense attornies found Aron is competent to stand trial. He had told his attorney he heard voices.