Levi Aron's lawyers said during the arraignment they would still consider an insanity defense and requested state Supreme Court Justice Neil Firetog keep Aron at New York's Bellevue Hospital Center for further evaluation and for his own safety.
Aron is accused of taking Leiby Kletzky, a Hasidic Jew, after the boy became lost walking home in Brooklyn from a day camp for the first time by himself and asked Aron for directions in July.
Parts of Leiby's body were later found stuffed in a suitcase and in a trash bin. The boy's feet were found in Aron's refrigerator and a set of bloody carving knives was recovered from his kitchen, police said.
Aron lawyer Pierre Bazile told reporters "we believe him to have some psychiatric disorders."
Brooklyn District Attorney Charles Hynes said in a statement: "Now that Mr. Aron has been found fit to proceed, we will move forward expeditiously to bring his case to trial. I want to reaffirm that this case will go to trial and that there are absolutely no circumstances which would lead me to accept a plea bargain."
Aron's next court appearance is set for Oct. 14. His lawyers said they intend to request a change of venue from Brooklyn.