NEW YORK (WABC) -- A suspect's confession to choking a 6-year-old boy to death in 1979 may be used at his murder trial, a judge ruled Monday, allowing prosecutors to use what appears to be their key evidence in one of the nation's most notorious missing children's cases.
Pedro Hernandez confessed two years ago to the abduction and killing of the Etan Patz, one of the first missing children ever pictured on a milk carton. Since then, his lawyer has insisted the confession was imaginary and that Hernandez is mentally ill.
The judge was not deciding whether the admissions were true, just whether Hernandez was properly advised of his rights, and whether he was mentally capable of waiving them.
Hernandez, 53, has pleaded not guilty to killing the boy, who vanished while walking to his school bus stop.
After decades of investigation that stretched as far as Israel, Hernandez emerged as a suspect only in 2012. He'd been a stock clerk at a store in Etan's neighborhood when the boy disappeared.
The Maple Shade, New Jersey, man confessed on video after more than six hours of questioning, telling police he lured Etan to the store basement with the promise of a soda, choked the boy, put the body in a bag and a box and left it on the street several blocks away.
"I was nervous, my legs were jumping," Hernandez says in the tape. "I wanted to let go, but I just couldn't let go. I felt like something just took over me. I don't know what to say. Something just took over me, and I was just choking him."
State Supreme Court Justice Maxwell Wiley called Hernandez's waiver of his Miranda rights "knowing and intelligent." While Hernandez has a very low IQ, his overall performance on tests of how well he understood the rights, his decision to waive them and "his basic ability to make his way in the world over a period of almost 40 years compel this conclusion," the judge wrote.
In the 1980s, Hernandez also allegedly told a prayer group and others that he'd harmed a child in New York.
The confession appears to be the key to the case. Authorities have not pointed to any physical or scientific evidence against Hernandez, and his defense has said there is none.
Jury selection is expected to start in early January, and Hernandez' attorney, Harvey Fishbein, stressed that it would be up to the jurors to decide whether the confession was true.
"We're looking forward to that, and we're ready to go," he said. "Anyone who sees these confessions will understand that when the police were finished with him, Mr. Hernandez believed that he killed Etan Patz - but that doesn't mean that he actually did."
Fishbein has said that Hernandez didn't have the mental capacity to understand his right to remain silent.
Hernandez' IQ, about 70, puts him in the bottom 2 percent of the population, a defense psychological expert testified during a weekslong hearing this fall.
Fishbein has said Hernandez's medical records mention schizophrenia dating back years, he has long taken anti-psychotic medication and since his arrest he's been diagnosed with schizotypal personality disorder. Its effects on him include "cognitive and perceptual distortions," including hallucinations, Fishbein has said. In one of the confessions, Hernandez says he has had visions of his dead mother.
Prosecutors say the confession was real and properly obtained.
Etan's body was never found. The day he vanished became National Missing Children's Day.
His father, Stan Patz, declined to comment as he left court Monday.
(The Associated Press contributed to this report.)