The K-159 sank in heavy weather, killing nine of the 10 crew members aboard. The vessel was being transported to the Polyarny shipyard on the northern Kola Peninsula in Russia’s northwest Murmansk region from the Gremikha Naval Base, taking with it 800 kilograms of spent nuclear fuel that were in its reactors when it sank in 240 metres of water. Suchkov, who was suspended as commander of Russia’s Northern Fleet after the incident, appeared at a military court with other officials, the BBC reported, though it was not immediately clear who else was with him.

Trial judge Alexander Khomyakov told reporters Mr. Suchkov had been charged with “negligence causing the death of one or more persons.” The trial at the naval base of Severomorsk, in Russia’s Far North, is being held behind closed doors to protect military secrets, according to Russian authorities. Khomyakov said 85 witnesses were expected to give testimony in hearings that could last several months, the BBC reported.

Russian President Vladimir Putin suspended Admiral Suchkov in September, amid allegations of a series of “preventable” mistakes.