Siarhei Kemezh is from Pružany, Brest region. On January 25, 2021, on the Vkontakte Russian social network, under the news about a criminal sentence for insulting the Minsk riot police commander, Kemezh posted an offensive comment about that policeman, which provoked the first criminal proceedings against him under Article 369 ('Contempt of a public official') and Part 1 of Article 208 ('Extortion') of the Criminal Code. 

His first case was tried by the Pružany District Court in September 2021. Judge Vadzim Mazol sentenced him to 24 months of freedom restriction and 3,000 Belarusian rubles of moral damages compensation. Besides, Siarhei Kemezh was accused of extorting. In total, he was sentenced to 2 years and 6 months of freedom restriction with a referral to an open-type penal facility. Veranika Manets supported the state prosecution in the case.

On June 19, 2023, in the Lida District Court (Hrodna region), Siarhei Kemezh was again tried under Article 369 of the Criminal Code ('Contempt of a public official') and sentenced to 24 months of imprisonment in a general-security penal colony and 100 base fines (that is 3,700 Belarusian rubles or approx. $1,224). Judge Ihar Kashko handed down the sentence suggested by Prosecutor Mikita Myslivets.

The second case against Siarhei Kemezh also stemmed from a comment he had posted on the Vkontakte Russian social network. The Brest-based Viasna branch believes that if Vkontakte had not disclosed Siarhei Kemezh's phone number indicated for a deleted account, he would not have been arrested.

In September 2022, Siarhei Kemezh was included in the 'List of extremists' with a note that he was serving his sentence.