Juvenile Justice Systems outlines options for shaping the juvenile liability models, in the form of model-patterns: the welfare model, the justice model, the rehabilitative treatment model, the restorative justice model, and different mixed models, especially the so-called "4xD formula." This comparative work consists of 4 parts, describing the general issues of juvenile criminal liability and characterizing three mixed models: the Polish, the Brazilian and the Portuguese. The comparison of three systems severely influenced by welfare ideas is seen as an innovative element of the presented...