Drug abuse is highly correlated with criminal behavior. The typical drug-using criminal commits hundreds of crimes per year. The crime rate cannot be significantly reduced without a reduction in the percentage of the population abusing drugs and alcohol. Accurate and timely estimation of that percentage is important for policy decisions concerning crime control, public health measures, allocation of intervention resources for prevention and treatment, projections of criminal justice needs, and the evaluation of policy effectiveness. Such estimation is particularly difficult because self reporting is unreliable; and physical testing has to date required blood or urine analysis which is expensive and invasive, with the result that too few people are tested. MIKOS Ltd. has developed a non-contact, passive technique with the potential for automatic, real- time screening for drug and alcohol use. The system utilizes thermal radiation which is spontaneously and continuously emitted by the human body. Facial thermal patterns and changes in patterns are correlated with standardized effects of specific drugs and alcohol. A portable system incorporating the collection and analysis technique can be used episodically to collect data for estimating drug and alcohol use by general unknown populations such as crowds at airports, or it can be used for repetitive routine screening of specific known groups such as airline pilots, military personnel, school children, or persons on probation or parole.