Since then, numerous Irish pedophiles have faced successful prosecution on even older charges, based mainly on victim testimony.
In the late 1990s, the Irish police investigated other child sex assault allegations against Mr. Gibney, but public prosecutors declined to press charges or seek his extradition, according to Justine McCarthy, a journalist for The Sunday Times of London and author of “Deep Deception,” a 2009 book about sexual abuse scandals in Irish swimming.
When asked for comment, the Office of the Director of Public Prosecutions, an Irish government agency, said it “does not comment on individual cases.”
No criminal complaints or charges have been brought against Mr. Gibney in the United States. But Ms. McCarthy said she had interviewed an Irish woman — once a prospect for Ireland’s Olympic swimming team — who said she had been raped by Mr. Gibney at a training camp in Tampa Bay, Fla., in 1991, when she was 17.
John D. Fitzgerald, a senior trial lawyer with expertise on Irish criminal and extradition law, said that were there to be new criminal charges in Ireland, this could potentially result in an extradition request under Ireland’s bilateral treaty with the United States. This application could then be contested in the American courts.
After leaving Ireland in 1994, Mr. Gibney sought to resume his career, first in Scotland — where he was forced to resign from his position at an elite swimming team in Edinburgh after an uproar from parents — and then in the United States.
After his case was dropped, he was able to enter the United States on a visa he obtained in 1992, soon after he was accused of abuse by two leading figures in Irish swimming — Francis White, a coach who said he was abused by Mr. Gibney, and the former Olympic swimmer Gary O’Toole, who heard about abuses from other swimmers — but before charges were brought.