Who Is Serhii Kuznetsov, The Ukrainian Ex-Officer On Trial Over Nord Stream?

Serhii Kuznetsov, a 50-year-old former Ukrainian military officer and special forces member, went on trial in Hamburg on Wednesday over the explosions that ruptured the Nord Stream gas pipelines connecting Russia and Europe. German prosecutors accuse him of helping lead a team that planted explosives on the seabed, in an operation they say was carried out on behalf of unidentified Ukrainian state entities. Kuznetsov denies involvement.

Who Is Serhii Kuznetsov?

Kuznetsov served in the Ukrainian military, including in its special forces, according to German public broadcaster. Before the trial began, German authorities had identified him publicly only as Serhii K under rules protecting the identity of criminal defendants.

His full name was reported publicly when the trial opened on Wednesday, as the anonymity restriction was lifted. He had been arrested in Italy in 2025 under a European warrant and later extradited to Germany.

Kuznetsov has been held in custody for nearly 11 months, much of that time in near-solitary confinement, his lawyers told the court. They argued that his conditions of detention had placed him under considerable strain. Prosecutors said he had indicated that the conditions were acceptable to him.

What Is He Accused Of?

German federal prosecutors allege that Kuznetsov helped organise and lead a group of Ukrainian operatives, including divers and an explosives expert, who carried out the pipeline sabotage in September 2022.

According to the prosecution, Kuznetsov travelled to Germany through Poland about three weeks before the explosions, allegedly using a forged Ukrainian passport. The group then hired a sailing yacht in Rostock and travelled towards the area near the Danish island of Bornholm, where specialised explosives were allegedly attached to the pipelines on the seabed.

The Hamburg Higher Regional Court admitted the indictment for trial in September. The charges include a suspected war crime involving an attack on civilian objects, causing an explosion, destroying structures and disrupting public services. The court said the preliminary evidence provided sufficient grounds to proceed; it has not determined Kuznetsov’s guilt.

The blasts on September 26, 2022, ruptured three of the four Nord Stream pipelines, releasing large quantities of methane into the Baltic Sea.

What Is His Defence?

Kuznetsov remained silent during the opening hearing. His lawyers challenged the proceedings and called for the case to be dismissed, arguing that he could not mount a proper defence because he was bound by obligations to keep Ukrainian military information secret.

His lawyer Nicola Canestrini argued that the pipelines were part of Russia’s economic and strategic infrastructure and could be considered legitimate targets in the context of Russia’s war against Ukraine.

“Is it unlawful to destroy an aggressor’s infrastructure without harming any human beings?” Canestrini asked, according to Reuters.

The defence also argued that the evidence did not establish Kuznetsov’s involvement in the attack. His lawyers questioned the legality of his extradition, saying he had been transferred from Italy on the basis of a sabotage investigation but was now facing a war-crime charge in Germany.

Why Does The Trial Matter?

The case is politically sensitive because Germany has continued to support Ukraine while investigating a sabotage operation that damaged infrastructure central to its former energy relationship with Russia. Kyiv has denied state involvement in the explosions, while Moscow has demanded that those responsible, including whoever ordered the operation, be identified.

Kuznetsov is the only person currently on trial in Germany over the blasts. Croatian authorities have separately arrested another man, identified as Vladimir Z, whom prosecutors believe may have been one of the divers involved.

The Hamburg proceedings are scheduled to continue into the coming months, with further hearings expected into early 2027. The trial could clarify some of the evidence surrounding the sabotage, but whether it will establish who authorised the operation remains an open question.