The Arkhangelsk regional court ruled on 16 December that Sergei Alekseichuk was guilty of causing the deaths of 58 people in 2004 by opening the gas valves of a nine-story apartment block. The court ruled that the defendant acted under the influence of alcohol.
The 27-year-old Alekseichuk, a former municipal gas employee, initially confessed to opening the valves. But he later retracted his words, saying investigators had coerced a confession from him.
His lawyers say they will appeal the verdict.