After the murder in a duel of the great Russian poet A.S. Pushkin was succeeded by M.Yu. Lermontov. Lermontov's death, just like Pushkin's - in a duel, shocked the Russian public. Various theories about a conspiracy to murder and unfounded speculation about the circumstances of the duel arose. The authentic materials of the criminal case brought to the attention of the reader allow us to establish many important circumstances of the duel between Lermontov and Martynov, form our own opinion about the duel, including finding out whether the rules of the duel were violated, and exclude a number of erroneous versions of what happened. In addition, these historical documents give an idea of how military court proceedings in the case were conducted at that time and what circumstances were taken into account when assigning punishment for participation in a duel.