After life imprisonment was reinstated as a penalty in Poland, 304 murderers were sentenced between 19 November 1995 and 31 December 2011. In this monograph, the authors present the results of their own research conducted between 2012 and 2017. The research involved: a criminological analysis of aggravated homicides and their perpetrators; an analysis of the judicial dimension of life imprisonment; and an analysis of the implementation of life imprisonment from the perspective of interested parties (the prisoners, prison staff , families of perpetrators and victims, the judiciary, and the public).