49-year-old Timo Kivimäki, a Finnish humanities professor at the University of Copenhagen, is accused of spying for the Russians and is being tried at the city court in Glostrup behind double-locked doors, meaning no information about the trial, including the precise charges, can be disseminated.

But following demands from both Kivimäki's lawyer and the Danish media, he has been granted permission to appeal against the decision to hold the trial in secret.

The decision to hold the trial in secret was made after both the Foreign Ministry and Justice Ministry argued that the trial's revelations could damage Denmark’s relationship with Russia.

Kivimäki’s lawyer Anders Nemeth wanted the trial to be held in public but both the city court in Glostrup and the Eastern High Court decided to follow the guidance of the ministries and hold the trial behind double-locked doors. The case's secrecy has now been appealed to the Supreme Court.

“The Supreme Court will not be able to make a ruling before the verdict is handed down on May 31,” Nemeth acknowledged to Ekstra Bladet. “But the Supreme Court’s verdict may set a precedent for future cases. If the Supreme Court decides that the doors may remain open then it will probably mean that the press will be given access to the court records from the case.”

The trial against Kivimäki started on May 8 and while his verdict and potential sentence will be publicised, the reasoning and evidence will remain secret.

Kivimäki was arrested in April and is being charged under anti-spy legislation on suspicion of having helped a foreign intelligence agency operate in Denmark. He faces up to six years in prison, though a 12-year sentence is also possible if military secrets have been shared.

Kivimäki has admitted to holding meetings with Russian diplomats and carrying out paid work for them, but he denies the accusation from domestic intelligence agency PET that he was prepared to provide the Russians with the names of students he thought were potential spy candidates.