This article aims to analyze the effect of the new drug law, in force since 2006, on the efficiency of incarceration in reducing the homicide rate. There exists a reasonable consensus in the literature that the incarceration rate is valid for reducing the homicide rate, i.e., arresting more offenders usually entails lower homicide rates. However, by hypothesis, since the new drug law does not make clearly differentiating between user and drug dealer, this could increase the punishment of drug users and weakened punishment to the trafficker. Hence, we test this hypothesis based on panel data econometric models considering data from Brazilian states between 2004 and 2014. Results from the econometric models show, based on empirical evidence, that with the new drug law there was increased the efficacy of incarceration in reducing the homicide rate, contrary to what we expected.