At first, Mr. Hernandez, 51, averted his eyes from the image of the 6-year old boy, who was last seen walking to school on May 25, 1979. But by the end of the interrogation, Mr. Hernandez had not only looked at the picture; he had also signed his name across it and even written a brief confession on the picture, one law enforcement official briefed on the investigation said.  “They had him sign on the photograph, and write, ‘I killed him’ or ‘I strangled him,’ ” said the official, who was granted anonymity to discuss evidence.  Police Commissioner Raymond W. Kelly has said that during questioning of Mr. Hernandez on May 23 in Camden, N.J., the suspect provided a lengthy videotaped confession in which he said he had lured Etan from his school bus stop, led the boy into the basement of the bodega where he worked, and strangled the child.  But the short handwritten statement of guilt on the picture may emerge as one of the more memorable courtroom exhibits if the case goes to trial, especially since the prosecution is likely to lack physical evidence tying Mr. Hernandez to the crime.  That the authorities sought a confession on an image of the boy suggests that in the absence of physical evidence, prosecutors and investigators sought visual evidence that might prove compelling to jurors.  Mr. Kelly has said investigators do not anticipate ever recovering the boy’s remains, which Mr. Hernandez has said he left out with the trash, a little more than a block from the bodega.  Even so, the Police Department has been in conversations with the Sanitation Department and private carting companies to try to discover where trash taken from SoHo after the Memorial Day weekend of 1979 would have been buried.  Mr. Hernandez’s lawyer, Harvey Fishbein, declined to comment.  Another official said Mr. Hernandez told investigators he had frequently been beaten as a child. That detail could prove significant to prosecutors struggling to account for possible motives.  Commissioner Kelly has said that Mr. Hernandez did not give a reason when he told investigators that he had killed Etan. Indeed, during the confession, investigators repeatedly sought an explanation from him, but even as he confessed to the crime, Mr. Hernandez was unable to say why he had done it or, at first, even to look at the image of Etan’s face.  “When they put the photo in front of him, he kept looking away,” the law enforcement official said.  The New York Post has reported that Mr. Hernandez wrote his name on Etan’s missing-child poster as a sign of guilt.  In the weeks since Mr. Hernandez’s confession, prosecutors and investigators have been searching for corroborating evidence and have interviewed relatives of Mr. Hernandez, who is charged with second-degree murder. “We need to make sure that accountability is levied as to the right person, and under appropriate evidence,” the Manhattan district attorney, Cyrus R. Vance Jr., told reporters last week.  Asked how confident he was that Mr. Hernandez had committed the crime, Mr. Vance said, “I’m not going to answer that question.”  He added: “And not because I’m afraid to answer it. Just because it’s really premature for me to answer it at this time.”  Starting Wednesday afternoon, the authorities searched Mr. Hernandez’s home in Maple Shade, N.J., which is near Camden, for more than 10 hours, said Robert Gottlieb, a lawyer for Mr. Hernandez’s wife, Rosemary.  Investigators removed a computer hard drive as well as papers belonging to Mr. Hernandez, Mr. Gottlieb said. During the search, Ms. Hernandez and her 23-year-old daughter, Becky, sat in the backyard, neighbors said.  Commissioner Kelly has said someone called the New York Police Department’s Missing Persons Squad in May to say that Mr. Hernandez had in the past confessed to killing a boy.  The tip came shortly after the Federal Bureau of Investigation and the Police Department dug up the basement of a building along Etan’s route to the school bus in a search for his remains. Although the search was fruitless, the effort had thrust the Patz case back into the news, which, Mr. Kelly said, led to the tip to the police.  Mr. Gottlieb said Ms. Hernandez “firmly believes the confession is unreliable and not believable.”  He added that Ms. Hernandez, who was interviewed at length by the police on the same day as her husband, “is incredulous that anyone would believe what he said, knowing his history of hallucinations and delusions, and other exhibited mental illnesses.”  During Mr. Hernandez’s arraignment, Mr. Fishbein, his lawyer, said the defendant had a lengthy psychiatric history, including diagnoses of schizophrenia and bipolar disorder, with visual and auditory hallucinations.  Russ Buettner and Nate Schweber contributed reporting.
When investigators showed Pedro Hernandez an image of Etan Patz, who had said he had killed, he looked away, but later wrote a confession on it, an official said.