The Brooklyn district attorney, Charles J. Hynes, has repeatedly said that since taking office in 1990, he has vigorously tried to extradite Mr. Mondrowitz. Mr. Hynes has said his office was instrumental in bringing about a change in a treaty between the United States and Israel in 2007 that had thwarted early extradition efforts.
But newly disclosed documents from Mr. Hynes’s office cast doubts on his accounts of his role in the case, suggesting that for many years, the office paid little attention to it.
Michael Lesher, a writer and lawyer who represents several of Mr. Mondrowitz’s accusers, obtained 103 pages of files on the case from the district attorney’s office after a protracted court battle to secure them under the state’s Freedom of Information Law.
Mr. Hynes has long been criticized by advocacy groups representing victims of child sexual abuse, who claimed that he was too accommodating of politically influential ultra-Orthodox Jewish rabbis, many of whom teach that such crimes should be handled by rabbinical authorities.
Scrutiny of his office intensified last month after articles in The New York Times raised questions about his handling of sexual abuse cases among the ultra-Orthodox.
Mr. Hynes has defended his record, but after the articles were published, he promised to push for legislation making it mandatory for rabbis to report abuse. He also set up a task force to crack down on witness intimidation, which has stymied many sexual abuse cases in the community.
The Mondrowitz case has long been one of the most notorious child sexual abuse cases in Brooklyn.
Mr. Mondrowitz was charged with molesting five boys, but Amy Neustein, editor of the book “Tempest in the Temple: Jewish Communities and Child Sex Scandals,” which includes a history of the case, said she believed he had at least 100 victims.
Mr. Mondrowitz, now 64, has denied the charges.
The first efforts to extradite Mr. Mondrowitz, made in the mid-1980s by Mr. Hynes’s predecessor as district attorney, Elizabeth Holtzman, failed after the Israeli authorities ruled that the extradition treaty did not cover sodomy.