The nature of the charges against Mr. Rezaian, 39, was not disclosed until last month, when his lawyer, Leila Ahsan, said they included espionage. Ms. Ahsan has been permitted to meet with Mr. Rezaian, a dual Iranian-American citizen, only once.

Image Jason Rezaian, a correspondent for the Washington Post, in Tehran in 2013. Credit... Vahid Salemi/Associated Press

The Iranian government is presenting two pieces of evidence of espionage, Mr. Rezaian’s brother, Ali Rezaian, said: an American visa application for Yeganeh Salehi, Jason Rezaian’s wife, an Iranian citizen and a journalist, and a form letter sent by Mr. Rezaian to Barack Obama’s 2008 White House transition team offering help to improve relations between Iran and the United States. It is unclear why the Iranian authorities believe those documents to be incriminating.

Judge Salavati has a reputation for tough sentences that led the European Union to place him on a blacklist in 2011 for human rights abuses. He has ignored foreign requests for court access.

“If Iran had a case against Jason Rezaian, it would try him in public,” Kenneth Roth, the executive director of Human Rights Watch, wrote on Twitter. “It doesn’t and won’t.”

The trial is expected to last two to three days, Ali Rezaian said in a telephone interview from California, where he and his brother were born and grew up, adding that the lawyer had told the family of the judge’s decision on court access only on Monday. He denounced the decision, calling it “unconscionable.”