By Natasja Sheriff

NEW YORK (Reuters) - Attorneys defending the man accused of murdering 6-year-old Etan Patz put the blame on Monday for the boy's 1979 disappearance on a convicted child molester who was a longtime suspect in the case.

Pedro Hernandez, 54, a former grocery clerk, is on trial for kidnapping and murder in a case that hinges on his confession in 2012 to police that he choked the boy, stuffed him in a box and left him in a New York alley.

Patz vanished as he walked alone for the first time to a school bus stop in his Manhattan neighborhood on May 25, 1979. His disappearance sparked a national movement to find missing children, with his picture one of the first to appear on milk cartons.

Defense lawyers say Hernandez's confession was coerced by police and that the real killer is Jose Antonio Ramos, whose girlfriend used to walk Patz to school and who for years was the prime suspect.

During questioning by the defense on Monday, former Assistant U.S. Attorney Stuart GraBois testified that Ramos told him during a 1988 interview that he took a young boy to his apartment for sex on May 25, 1979. Ramos told GraBois he was “90 percent sure” the boy was Etan Patz.

When the boy resisted, Ramos said, he put him on a subway to visit an aunt, GraBois testified in state court in Manhattan.

GraBois led the investigation into the boy’s disappearance from 1985 to 1991.

Earlier, jurors watched a videotaped interview of Ramos, following his arrest in 1982 after two young boys reported that he tried to lure them into a drainpipe in a Bronx park, where he was living at the time.

In the video, Ramos says his girlfriend used to take care of Patz but that he never met him.  

Ramos served 27 years in a Pennsylvania prison for the rape and molestation of three young boys in the 1980s. Shortly after his release in 2012, he was rearrested for breaking sex offender registration laws, and returned to prison.

A judge found Ramos legally responsible for the death of Patz in a 2004 civil suit brought by the Patz family.

(This story corrects date of Ramos interview to 1988 from 1985 in 5th paragraph)

(Editing by Barbara Goldberg and Peter Cooney)