YEKATERINBURG, Russia (AP) — Closing arguments began Friday in the espionage trial of U.S. journalist Evan Gershkovich, who has been held behind bars for over a year on charges that he, his employer and the U.S. government vehemently deny.

Gershkovich appeared in court for a second straight day as the proceedings in Russia’s highly politicized legal system picked up speed. Unlike previous sessions in which reporters were allowed to see Gershkovich briefly before the proceedings began, there was no access to the courtroom this week and he was not seen, with no explanation given. Espionage and treason cases are typically shrouded in secrecy.

Gershkovich, 32, was arrested March 29, 2023, while on a reporting trip to the Ural Mountains city of Yekaterinburg. Authorities claimed, without offering any evidence, that he was gathering secret information for the U.S. The American-born son of immigrants from the USSR, Gershkovich is the first Western journalist arrested on espionage charges in post-Soviet Russia.

“Evan’s wrongful detention has been an outrage since his unjust arrest 477 days ago, and it must end now,” the Journal said Thursday in a statement. “Even as Russia orchestrates its shameful sham trial, we continue to do everything we can to push for Evan’s immediate release and to state unequivocally: Evan was doing his job as a journalist, and journalism is not a crime. Bring him home now.”

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The U.S. State Department has declared Gershkovich “wrongfully detained,” committing the government to assertively seek his release.

Gershkovich faces up to 20 years in prison if found guilty, which is almost a certainty in Russia’s highly politicized legal system. Russian courts convict more than 99% of defendants, and prosecutors can appeal sentences that they regard as too lenient. They even can appeal acquittals.

Russian Foreign Minister Sergey Lavrov on Wednesday reaffirmed the Kremlin claim of “irrefutable evidence” against Gershkovich, although neither he nor any other Russian official has ever disclosed it. Lavrov said Wednesday at the United Nations that Moscow and Washington’s “special services” are discussing an exchange involving Gershkovich. Russia has previously signaled the possibility of a swap, but it says a verdict would have to come first.

State Department deputy spokesman Vedant Patel on Thursday declined to discuss negotiations about a possible exchange, but said: “We have been clear from the get-go that Evan did nothing wrong and should not have been detained. To date, Russia has provided no evidence of a crime and has failed to justify Evan’s continued detention.”

U.S. Ambassador to the U.N., Linda Thomas-Greenfield accused Moscow of treating “human beings as bargaining chips.” She singled out Gershkovich and ex-Marine Paul Whelan, 53, a corporate security director from Michigan, who is serving a 16-year sentence after being convicted on spying charges that he and the U.S. denied.

Gershkovich’s trial began June 26 in Yekaterinburg after he spent about 15 months in in Moscow’s notorious Lefortovo Prison.

At the trial’s first day, the court said it was adjourning until mid-August but it later changed track and rescheduled hearings for this week after Gershkovich’s lawyers asked for them to be held earlier, according to Russian news reports.

The Russian Prosecutor General’s office said last month the journalist is accused of “gathering secret information” on orders from the CIA about Uralvagonzavod, a plant about 150 kilometers (90 miles) north of Yekaterinburg that produces and repairs tanks and other military equipment.

Gershkovich’s employer and U.S. officials have dismissed those charges as fabricated and denounced the trial as illegitimate and a sham.

“Evan has never been employed by the United States government. Evan is not a spy. Journalism is not a crime. And Evan should never have been detained in the first place,” White House national security spokesperson John Kirby said last month.

Russia’s interpretation of what constitutes high crimes like espionage and treason is broad, with authorities often going after people who share publicly available information with foreigners and accusing them of divulging state secrets.

Earlier this month, U.N. human rights experts said Russia violated international law by jailing Gershkovich and should release him “immediately.”

The Working Group on Arbitrary Detention that includes independent experts convened by the U.N.’s top human rights body, said there was a “striking lack of any factual or legal substantiation” for spying charges leveled against Gershkovich. It said his U.S. nationality has been a factor in his detention, and as a result the case against him was discriminatory.

Arrests of Americans are increasingly common in Russia, with nine U.S. citizens known to be detained there as tensions between the two countries have escalated over fighting in Ukraine.