The man charged with killing a 6-year-old New York City boy in 1979 pleaded not guilty Wednesday to murder, even though police say he confessed in the sensational case - an admission his attorney says is false.

Pedro Hernandez, 51, wore a gray sweat suit and answered "not guilty" at the hearing in the notorious case of Etan Patz, whose disappearance helped spawn the movement to publicize cases of missing children.

Hernandez's defense will revolve around his mental state, but he isn't pursuing an insanity defense, his attorney, Harvey Fishbein, has said.

An insanity defense would mean acknowledging that he committed the crime but arguing that he was too psychologically ill to know it was wrong. Hernandez will maintain that he didn't kill Etan Patz and will argue that he made a false confession because of his mental problems, among other factors, Fishbein said.

"The only part that mental disease plays in this case is its role in the confession," he said.

- Associated Press