Attrition refers to the loss of cases throughout the criminal justice system process. It occurs along the entire criminal justice chain, from detecting and registering crime, to identifying a suspect and prosecuting, convicting and sentencing this suspect. For example, a lack of physical evidence or witnesses can make it impossible to identify a suspect or proceed to prosecution. This is particularly harmful in the case of serious crimes committed by organized criminal groups considering their negative economic and social implications. Transnational organized crimes, such as drug trafficking, trade in protected species of fauna or flora, trafficking in persons or offences against cultural property, are especially consequential and should never go unpunished.

The International Classification of Crime for Statistical Purposes (ICCS) provides a comprehensive framework for producing high-quality statistics on crime and criminal justice. The ICCS was endorsed by the United Nations Statistical Commission at its 46th session in March 2015 as the international statistical standard for data collection. It offers a set of discrete, exhaustive, and mutually exclusive categories and, as such, reasonably covers every manifestation of crime. This includes crimes that are often organized and transnational in nature, such as trafficking in persons and drug trafficking (see report table 1).