Iran's Supreme Court annulled the death sentence after Hekmati appealed, ordering a retrial in 2012. The country's Revolutionary Court then overturned his conviction for espionage, his lawyer Mahmoud Alizadeh Tabatabaei told The Associated Press. Instead, it charged him with "cooperating with hostile governments" and sentenced him to 10 years in prison, Tabatabaei said.
Iran's Appeals Court "recently" upheld the verdict, the lawyer said, a decision that is final.
Tabatabaei said he is seeking Hekmati's conditional freedom from Evin prison, north of the capital, Tehran. Hekmati has been behind bars since his arrest.
"According to law, if someone serves one-third of his conviction period and within that time, shows an acceptable behavior in jail, he can be entitled to conditional freedom," Tabatabaei said. "One-third of his imprisonment will end around September and October."
Conditional freedom could allow Hekmati to leave the country, depending on what a court decides. That could allow Hekmati to visit his father Ali Hekmati, a professor at Mott Community College in Flint, Michigan, who family members say has been diagnosed with terminal brain cancer and recently suffered a stroke.
Tabatabaei said a doctor treating Hekmati's father at a U.S. hospital has sent him a letter asking the ex-Marine's leave on bail to meet his ailing father
"We have requested that if the prosecutor agrees, Amir can go on leave with an appropriate bail so that he could go and visit his father," Tabatabaei said.
The Obama administration in November asked for Iran to free Hekmati and two other Americans believed held there, as relations recently have thawed between Washington and moderate President Hassan Rouhani. The call comes as world powers continue negotiations with Iran over its contested nuclear program.
A family representative in Michigan did not return a call for comment Saturday. U.S. Rep. Dan Kildee, a Flint Democrat who represents Hekmati and his family in Congress and has worked to free him, said in a statement that releasing him would be "a tangible demonstration by Iran that it is serious about rejoining the global community."
"He is innocent and has committed no crime," Kildee said. "He is an American citizen who, with the permission of the Iranian government, traveled to Iran to simply visit his grandmother for the first time. He has been wrongfully imprisoned for 956 days."
Tabatabaei said he hadn't met face to face with Hekmati, but remained "constantly in contact with him."
"His morale is good," the lawyer said.
Associated Press writer Corey Williams in Detroit contributed to this report.