The current drug legislation established certain criteria to distinguish the crimes of drug use and trafficking, creating two different models of state response to these crimes. This research focuses on sentences related to drug trafficking crimes in order to understand how judges draw a distinction between drug users and drug traffickers. We have analyzed a sample of all the first instance sentences from the Court of the State of Rio de Janeiro in 2015 in order to establish a series of categories which allow judges to justify their decisions in drug trafficking cases. This research is an empirical qualitative legal research based on document analysis as the basic research technique. The analysis of the data was conducted through a grounded theory framing and the results point to the key role of the witnesses in the decision-making process of the judges.