The trial of the three U.S. nationals charged with “espionage and illegal entry in to Iran” began today in Tehran behind closed doors. The trial comes at a time of tense relations between Tehran and Washington over nuclear negotiations.

Sarah Shourd, Shane Bauer and Josh Fattal were arrested in the border regions of Iran-Iraq in the summer of 2009. They maintain they were hiking in Iraq’s mountains and if they trespassed into Iranian territory it was inadvertent.

Iran released Shourd last September on $500,000 bail for medical reasons. She is currently in the U.S., but the two others remain in Tehran’s Evin Prison.

Last week, when prosecutor, Gholamhossein Mohseni Ejei announced today’s trial date, Iran officially demanded that Shourd return to stand trial, but she remains in the U.S. Iran says the bail money will be confiscated if Shourd does not return.

Massoud Shafii, the lawyer for the three Americans, told the French News Agency on Saturday that so far he has been prevented from meeting with his clients to prepare for today’s trial.

Shafaii said he will argue that his clients are innocent and the spying charges were “irrelevant.” He added that Iran’s penal code allows for a prison sentence of up to three years on the charge of illegal entry, but that could also be commuted to a fine.