"For a drug court program, drug testing is conducted primarily to monitor a defendant’s progress in treatment — to determine whether he or she has been using drugs and, if so, the type and quantity of substances being ingested. The drug test result may be used as a basis for imposing sanctions and/or enhancing treatment services, on the one hand, or reducing treatment service requirements, on the other. Drug test results may also indicate a participant’s progress in reducing drug use when he or she has not eliminated it altogether.
"Although drug test results are frequently reported in terms of 'positive' or 'negative,' in reality, the determination of the presence or absence of a particular drug in the system is not always a black-and-white determination. Ultimately, for a drug court program, a positive or negative result reflects the presence or absence of certain drug metabolites in the sample at a concentration above or below the established cutoff concentration."
Robinson, Jerome J. and Jones, James W., "Drug Testing in a Drug Court Environment: Common Issues to Address," part of the Drug Court Resource Series, Drug Court Clearinghouse and Technical Assistance Project of American University (Washington, DC: Office of Justice Programs, U.S. Department of Justice, May 2000), p. 2.