International Narcotics Control Board (INCB) Annual Reports
Global drug situation, analyses of trends in drug abuse and drug trafficking
National Criminal Justice Research Service (NCJRS)
The NCJRS Abstracts database is a great place to search for criminal justice related information covering US and international sources and issues. Some are available as Full-Text.
UN Interregional Crime and Justice Research Institute (UNICRI)
The UNICRI Documentation and Information Centre has a comprehensive collection of data.
UNODC Homicide Statistics
The dataset covers 207 countries and territories and provides data on homicide levels, trends and contextual characteristics.