It was just before 1 p.m. on Friday when 11 jurors who were part of one of the longest deliberations in recent years gave up any hope of swaying the 12th person on the panel.

For 18 days, the jurors had sat elbow to elbow around a rectangular table inside the State Supreme Court building in Lower Manhattan, trying to reach consensus on whether a man committed a notorious crime: the abduction and murder in 1979 of a 6-year-old boy, Etan Patz, who vanished while walking from his family’s SoHo loft to a school bus stop two blocks away.

The defendant, Pedro Hernandez, 54, had confessed to killing Etan almost 33 years after he disappeared, but there was no physical evidence tying him to the crime. Defense lawyers argued that the confession, which he repeated later to a prosecutor, was a fiction made up under police pressure by a man with a low I.Q. and a personality disorder clouding his ability to tell fact from fantasy.

On Friday morning the jurors found themselves focusing again on what many had considered one of the most damning bits of evidence against Mr. Hernandez: that he had provided physical details of a passageway on Thompson Street where he said he had dumped Etan’s body. They listed possible explanations for that knowledge on a small whiteboard.