By Natasja Sheriff

NEW YORK (Reuters) - Jurors in the New York murder trial of a man who confessed to killing 6-year-old Etan Patz decades ago ended their 12th day of deliberations on Thursday without a verdict.

The jury, which is weighing kidnapping and murder charges against Pedro Hernandez, was set to resume its discussions for a 13th day on Friday at state Supreme Court in Manhattan.

Patz's 1979 disappearance from his Soho neighborhood in Manhattan brought national attention to the issue of missing and abducted children. He was one of the first children whose pictures appeared on milk cartons in an effort to find them.

In 2012, Hernandez, a 54-year-old former deli worker, confessed to police that he had choked Patz, stuffed him in a box and left his still-moving body in an alley.

But his attorneys argued that Hernandez is mentally ill and his confession was coerced by police.

The jury spent much of Thursday reviewing the defense's closing argument for acquittal. That included viewing several defense exhibits projected on two large video screens, such as excerpts of Hernandez's confession, police records detailing investigations after Patz went missing and criteria that mental health experts used to diagnose Hernandez with Schizoptypal Personality Disorder.

Jurors were ordered back to work by Justice Maxwell Wiley after telling him on Wednesday that they were deadlocked and could not reach a verdict.

Patz vanished on May 25, 1979 as he walked alone for the first time to a school bus stop. The crime long haunted New Yorkers who can recall the massive search for the missing blond boy, who was never found. He was declared dead in 2001.

Hernandez's defense attorneys have put the blame for the boy's disappearance on Jose Ramos, whose girlfriend walked Patz home from school and who was long considered the prime suspect.

Ramos, convicted of sexually abusing boys, is serving a prison term in Pennsylvania.

Hernandez's wife, Rosemary, and daughter, Becky, have been present in court throughout the jury's deliberations.

Patz's father, Stan Patz, who was present throughout the trial, has been absent from court since the jury began deliberations.

If the jury stalemate holds and a mistrial is declared, the prosecution will have to decide whether to retry the case.

(Editing by Barbara Goldberg and Jonathan Oatis)