NEW YORK - Thirty-three years to the day after 6-year-old Etan Patz vanished without a trace while walking to catch a school bus, a man accused of strangling him and dumping his body with the trash was arraigned on a murder charge on Friday in a locked hospital ward where he was being held as a suicide risk.

A lawyer for Pedro Hernandez, who was a teenage convenience store stock clerk at the time of the boy's disappearance, told the judge that his client is mentally ill and has a history of hallucinations.

Hernandez, now 51, appeared in court on Friday evening via video camera from a conference room at Bellevue Hospital, where he was admitted earlier in the day after making comments about wanting to kill himself.

The legal proceeding lasted only around 4 minutes. Hernandez didn't speak or enter a plea, but his court-appointed lawyer, Harvey Fishbein, told the judge that his client was bipolar and schizophrenic and has a "history of hallucinations, both visual and auditory."

A judge ordered Hernandez held without bail and authorized a psychological examination to see if he is fit to stand trial.

Hernandez was expressionless during the hearing. He wore an orange jumpsuit and handcuffs. A police officer stood behind him.

The prosecutor who appeared in court, Assistant District Attorney Armand Durastanti, said it was "33 years ago today that 6-year-old Etan Patz left his home on Prince Street to catch his school bus. He has not been seen or heard from since. It's been 33 years, and justice has not been done in this case."

Hernandez, a churchgoing father now living in Maple Shade, N.J., was arrested Thursday after making a surprise confession in a case that has bedeviled investigators and inspired dread in generations of New York City parents for three decades.

Even with evidence as compelling as a full confession to murder, prosecutors making the case Hernandez killed Patz in Manhattan 33 years ago have their work cut out for them, legal experts said Friday.

Police say they have little evidence besides the confession so far, and in New York a confession alone is not enough to win a conviction.

"Starting now, they're going to try to corroborate every syllable of that confession," said Frank Schroeder, a former prosecutor in Nassau's Major Offense Bureau. "If he says he took the child to a basement and there was a sink in the corner, they're going to have to find out whether there was, in fact, a sink there."

Under state law, a confession alone isn't sufficient to obtain a criminal conviction. That's because innocent people have been known to confess to crimes, said Richard Klein, a criminal law professor at Touro Law School in Central Islip.

In some cases, police have elicited false confessions out of suspects. In others, people have spontaneously confessed to crimes they didn't commit because of mental illness or a craving for infamy, lawyers and experts said.

"Our instinct is always to say, 'He confessed. What more do you need?' " Klein said. "But people can have all kinds of motivations for falsely confessing to a crime."

Investigators will need to show that Hernandez, 51, was in the neighborhood the day Etan went missing, and that he had opportunity to commit the crime. Then they have to back up any details Hernandez gave about how and where he committed the crime, experts said.