The unit is responsible for determining patterns of drug use and drug dealing on the streets. The research is conducted by a carefully selected multiracial team of ex-addicts. Unit personnel obtain data on drug trafficking by observing, eavesdropping, and asking questions on the street. Because of the backgrounds of team members, their information is cross-referenced to determine accuracy, and their work habits are monitored by the unit coordinator. The unit has done over 200 studies in the last 18 years. The unit was the first to report the use of 'black tar,' heroin coming mainly from Mexico; the smoking of bazooka paste; and the use of two pills taken together to produce an effect similar to that given by heroin. The unit also identified the extensive use of 'crack' and has documented drug use on Wall Street. Unit members do not act as informers against particular persons but exchange information with law enforcement agencies to assist them in the development of drug law enforcement strategies.