New York (CNN) -- The man who confessed to the 1979 murder of 6-year-old Etan Patz was indicted Wednesday by a Manhattan grand jury, authorities said.
His attorney, Harvey Fishbein, said Pedro Hernandez -- who was arrested on second degree murder and kidnapping charges -- is scheduled to appear in court Thursday.
"Nothing that occurs in the course of this trial will answer what actually happened to Etan Patz," said Fishbein, who said his client has been "repeatedly diagnosed as suffering from schizophrenia."
"Partly as a result of that disorder, my client has an IQ in the borderline-to-mild mental retardation range," he said. Fishbein had previously told a judge that Hernandez has a history of mental disorders, suffers from hallucinations and is bipolar.
But district attorney spokeswoman Erin Duggan said Wednesday's indictment was "the outcome of a lengthy and deliberative process, involving months of factual investigation and legal analysis."
"We believe the evidence that Mr. Hernandez killed Etan Patz to be credible and persuasive, and that his statements are not the product of any mental illness," she said.
This summer, he admitted that he choked the boy after luring him into the basement of a small Manhattan grocery store, police said.
Hernandez allegedly told authorities that he threw away the boy's body in a garbage bag. The remains have not been found.
After attending high school in the Camden, New Jersey, area, Hernandez moved to Manhattan at the age of 18, sharing an apartment in the city's SoHo neighborhood with his older sister.
He then took a job as a stock clerk at a corner convenience store in Lower Manhattan for about a month before returning to his mother's south Jersey home in the summer of 1979, according to family members and police.
Etan disappeared roughly a month earlier, on May 25.
Describing Hernandez as having been a quiet young man, relatives say his demeanor changed upon his return to New Jersey. He grew further withdrawn while also frequently becoming ill, they said.
Though his whereabouts after 1979 remain murky, family members say he at one point returned to New York. It's unclear for how long.
Patz disappeared on his way to a New York school bus stop more than 33 years ago. The boy's plight catapulted concern for missing children to the national forefront after authorities put his image on thousands of milk cartons.