Tehran, Iran (CNN) -- The trial for three American hikers charged with spying in Iran should proceed even if freed hiker Sarah Shourd fails to return for the next hearing, their attorney told CNN on Sunday.
Masoud Shafii said the court told him the next hearing for Shourd, Josh Fattal and Shane Bauer would be held May 11 at Branch 15 of the Revolution Court.
The three were arrested in 2009 for allegedly entering Iran illegally while hiking in Iraq's Kurdistan region. They have been charged with spying.
Shourd was released on $500,000 bail last year because of a medical condition and immediately left the country. She failed to return for a previous court hearing in February.
According to Shafii, Iran's foreign ministry has sent a summons to Shourd to appear in court on May 11, adding that it was "up to Sarah" on whether to return to Iran.
"Last time the trial was postponed because Sarah did not show up," Shafii said. "I hope this time the court separates her case from my other two clients, so that their trial can take place."
Iranian authorities have said Shourd will be tried in absentia if she doesn't appear in court.
All three defendants have pleaded not guilty. Fattal and Bauer continue to be held in Iran's notorious Evin prison.
According to Iranian law, Shafii said, the cases "should be separated so the trials can go on."
"I brought this to the attention of the court last time, but the court took no notice of my request," Shafii said.
He also said that he has been unable to meet with Fattal and Bauer despite getting the court's consent to do so.
"My efforts to see my clients before the trial resumes have been unsuccessful for the last couple of weeks," Shafii said. "I am still waiting for the authorities to call me and tell me to go see my clients."