In July 1988, he was sentenced to death for the murder of four boys, which was later commuted to 25 years in prison.
[2] On 4 July 1988, after his release from prison in connection with the care of his sick mother, Trynkiewicz lured 13-year-old Wojciech Pryczek into his apartment, strangled him, and then buried his corpse in the forest.
[3][4] During his trial, Trynkiewicz was found to be sane, and his behaviour was marked by the realization of sadism and sexual attraction combined with algolagnia.
[3] On 3 March 2014, a court decided to isolate him at an asylum in Gostynin (Krajowy Ośrodek Zapobiegania Zachowaniom Dyssocjalnym [pl]).
[6] On 6 April 2021, the Gostynin District Court sentenced Mariusz Trynkiewicz to six years of imprisonment for repeated possession of child pornography.