A U.S. man absolved of killing his Nicaraguan girlfriend was under guard at a police hospital Tuesday while struggling to obtain his release from custody, according to his lawyer.

A Nicaraguan appeals court on Monday overturned a 30-year sentence imposed on 28-year-old Eric Volz, of Nashville, Tenn., and ordered his immediate release.

Volz's lawyer, Fabbrith Gomez, accused officials of "a big delaying tactic" to keep him from being freed before prosecutors can appeal his freedom to the Supreme Court.

The judge who convicted Volz received the order to release him, but sent the file back to the appeals court in the city of Granada, "supposedly because the pages were not numbered correctly," Gomez told The Associated Press in a telephone interview.

"But in Granada, they say they haven't received anything," Gomez complained.

Prosecutors said Monday they would appeal the decision that cleared Volz, but the process could take several days.

"It's our understanding that if Nicaragua continues to hold Eric, a free man in the eyes of the court, for an impending appeal from the Supreme Court, that is against Nicaraguan law," said Melissa Campbell, spokeswoman for Volz's family, in a statement e-mailed to The Associated Press.

Volz was being treated for kidney stones, Gomez said. Volz and a Nicaraguan man, Julio Martin Chamorro, were sentenced in February for the death of Doris Ivania Jimenez, 25, who was found raped and strangled in November 2006 in a clothing store she owned in Rivas, 55 miles south of Managua. The appeals court upheld Chamorro's conviction.

Volz's family and friends say they are worried for his safety. After hearing that his conviction was overturned, some Nicaraguan radio stations urged people "to take justice into their own hands," according to a statement on the "Friends of Eric Volz" Web site.

Volz has proclaimed his innocence from the beginning, saying he was in Managua, two hours away from Rivas, when the crime occurred. At that time, Volz had lived for two years in Nicaragua, where he founded a bilingual magazine called "El Puente," or "The Bridge." He also worked as a real estate broker.

U.S. State Department spokesman Tom Casey told reporters that U.S. officials "are continuing to be in contact with the Nicaraguan authorities on this and urging them to implement the court's decision without delay."

"At the moment, we believe that there's not an immediate cause for concern," he said, noting that it often takes two to three days for Nicaraguan court decisions to be carried out.

"Our message to the Nicaraguan government is: We want to see this decision implemented as quickly as possible, want to see him be able to depart the country and return to his family."