Sergei was detained in March 2021 in St. Petersburg at the request of the Belarusian prosecutor's office, as he was wanted in a criminal case opened after a protest that took place on June 19, 2020, in Molodechno. He was with several dozen city residents who tried to prevent the detention of participants in the peaceful assembly. Sergei spent six months in a pretrial detention center in Russia, but was then deported to Belarus and convicted of "resisting riot police."
He was released in November 2023, having fully served his sentence as determined by the court.
