Former New Mexico Gov. Bill Richardson failed this week in his effortsto persuade the Cuban government to release a U.S. subcontractor serving 15 years in prison. But his attempt may have come at the worst possible time.

This week marked 13 years since the U.S. imprisonment of five Cuban nationals who were convicted of espionage and related charges in Miami. Their release is a cause celebre in Cuba, whose government says they were subjected to an unfair trial and were wrongly convicted. For years, pictures of the “Cuban Five” have been splashed on billboards and posters in Havana.

As Richardson was seeking to meet with Alan Gross, who was arrested in December 2009 for trying to distribute satellite telephone and Internet equipment to Cuba’s small Jewish community, the Cuban government on Monday was holding a massive gala in the Cuban capital, where the families of the five were treated as heroes and victims. Senior officials called the prisoners’ treatment “inhumane and cruel” and again demanded their release.

“The case of the Five is irrefutable evidence of Washington’s complicity with terrorists,” said Ricardo Alarcon, president of the Cuban National Assembly. The current U.S. administration, he said, will have to decide whether it wants to continue the “immoral cynicism” of its predecessors.

The five had infiltrated anti-communist Cuban exile groups, many of which have long been committed to overthrowing the island government by force. (Four members of one of the groups, Brothers to the Rescue, were killed in 1996 as their plane was shot down by Cuban jets while flying away from the island.) Prosecutors contended at trial that the five were also attempting to spy on the Miami-based U.S. Southern Command and the Naval Air Station at Key West.

Defense attorneys had petitioned for a change of venue, arguing that the five could not get a fair trial in Miami, where Spanish-language media coverage and public opinion in the exile community violently denounced them.

The defense lost that argument, but a three-judge panel for the United States Court of Appeals for the 11th Circuit, in Atlanta, later agreed unanimously that the trial had been unfairly held in Miami. The U.S. government then appealed, and the decision was overturned by the full 11th Circuit. The U.S. Supreme Court refused to hear the defendant’s subsequent appeal.

A new round of appeals is currently pending, with lawyers for the five re-arguing the venue question, in part on grounds that U.S. government funds paid for some of the overwhelmingly negative local media coverage during their trial. Many of the journalists who wrote scathing articles in Miami’s Spanish-language press were also employed by the government’s Radio Marti, which sends largely critical broadcasts to Cuba from Miami.

Over the years, the Cuban government has repeatedly referenced the case whenever the question of improved U.S.-Cuban relations has arisen. There are support groups for the five in this country, and they have won the support of a number of foreign government.

On a visit to Cuba in April, former president Jimmy Carter met with Cuban political prisoners and Gross and appealed for their release. He also met with families of the five, telling a Havana news conference that their continued detention “makes no sense” and expressing hope that “in the near future they will be freed to return to their homes.”

One of them, Rene Gonzalez, is scheduled for release Oct. 7 after serving 10 years for acting as an agent of a foreign government without notifying the U.S. attorney general. Gonzalez, a Chicago-born U.S. citizen who infiltrated Brothers to the Rescue, is subject to three additional years of probation but has petitioned to be allowed to return to Cuba to be with his family, and out of fear for his safety in Miami.

Prosecutors have asked the court to deny his petition on grounds that U.S. law requires he serve at least one year of probation before the remainder can be canceled. Gonzalez’s request to transfer his U.S. government supervision to the Cuban government is also invalid, prosecutors have said, because he is not eligible to make such an appeal until he is actually released. Additionally, they have questioned whether Cuban law enforcement supervision would meet U.S. standards.

One option is for Gonzalez, who also holds a Cuban nationality, to renounce his U.S. citizenship, making him eligible for deportation. In a news conference marking the 13th anniversary of his imprisonment Monday, Gonzalez’s attorney, Phil Horowitz, said that was currently unacceptable.

“If Rene were to renounced his U.s. citizenship before his release, while in the United States…he would have to go through deportation proceedings” and remain incarcerated until they were finished, Horowitz said.

“My client’s position is that he is willing to renounce if that allows him to have dinner with his family at home in Cuba on Oct. 7,” he said.