A couple from Russia’s western exclave of Kaliningrad is on trial for treason over the appearance of a secret agent in their wedding photographs, the Kommersant business daily reported Tuesday.

Baltic affairs expert Antonina Zimina and her husband Konstantin Antonets were arrested in 2018 on suspicion of sharing secret information with neighboring Latvia’s intelligence agencies, according to Kommersant. Authorities concluded the investigation in late 2019 and formally indicted Zimina and Antonets, Russian news agencies reported Monday.

Zimina and Antonets face up to 20 years in prison for blowing the cover of a Federal Security Service (FSB) counterintelligence officer who is Zimina’s old classmate, her father Konstantin Zimin told Kommersant. He identified the officer as Maxim without disclosing his last name.

Zimin alleges, however, that Maxim blew his own cover by speaking openly about his work, handing out business cards and taking photos with guests at Zimina and Antonets’ wedding in 2015.

The photographs were reported to have appeared on social media and, later, on Baltic television.

“No one thought it was a crime because Maxim made no secret of his work,” Zimin was quoted as saying.

He voiced frustration with the authorities for not interrogating other guests at the wedding and not summoning Maxim as a witness in the case.

Zimina and Antonets deny their guilt. Kommersant reports that neither of them have access to state secrets.

Russia has had tense relations with its three Baltic neighbors — all currently EU and NATO members — since the Soviet collapse and Moscow’s annexation of Crimea from Ukraine.