Sergei Lapin, also known as « Kadet », served in Grozny, Chechnya, as a lieutenant in the Russian special police detachment (OMON) from the Khanty-Mansiiskii region.
On 2 January 2001, Lapin and another official, whose identity remains unknown, took 26 year-old Chechen student Zelimkhan Murdalov to the police station in the district police of Oktyabrsky. During his detention, Murdalov was beaten with a truncheon and subjected to electric shock treatment in order to obtain his collaboration with the police forces. According to witnesses, Murdalov lost consciousness several times during the interrogation. On the next day, he was transferred to another cell and since then, his fate remains unknown. He is believed to have been tortured to death and is now one of thousands of people who have become victims of forced disappearances in Chechnya.
In September 2001, the journalist Anna Stepanovna Politkovskaya published an article where she wrote about allegations connecting Lapin to the disappearance and torture of Murdalov. Following the publication of the article, she received letters containing threats to her life. Lapin was suspected to have written these letters and a criminal investigation was opened in October 2001.
In January 2002, Lapin was arrested and charged in connection with the allegations of disappearance and torture of Murdalov.