How do socially relevant attributes influence juvenile criminal sentencing? While judicial decisions should, in principle, be fully based on legally relevant factors such as the seriousness of the offense and the defendant’s criminal record, I ask whether and how extralegal characteristics related to the adolescent’s position in structural relations affect the decision-making process. I propose a mixed-methods design to study mechanisms of criminal sentencing. Using data from a representative sample of the São Paulo juvenile justice system records, I estimate mixed-effects logistic models to assess the probability of being sentenced to confinement given certain extralegal attributes, while controlling for legally relevant variables. Interaction effects show that adolescents registered as full-time students and classified as drug users are more likely to be sentenced to confinement than their counterparts, even when the arraignment is the same. The second step involved weekly visits to the juvenile courthouse in São Paulo over four months to observe judicial hearings. Prosecutors are central to the decision-making process. The standard decision-making mechanism is based on police documents and legally relevant information. When there is a rupture in the definition of the situation (usually when non-minority defendants enter the courtroom), a new mechanism emerges and more lenient decisions are made.