Book excerpt: Although alcohol-related impaired driving continues to be the primary cause of fatal automobile accidents in the United States, drug-impaired driving has emerged as a growing threat to public safety. Identifying and prosecuting cases of driving under the influence of drugs (DUID) requires the engagement of three important actors within the criminal justice system: law enforcement, forensic toxicologists, and prosecutors. Each of these actors plays a crucial role in gathering, interpreting, or presenting evidence of drug-impaired driving to build a successful case. Meticulous observational and chemical evidence collection and skilled, simple interpretation of this evidence is particularly important in a DUID case because such cases can be more complex and difficult to prove than alcohol-related impaired driving cases. Although blood alcohol concentration levels have been established and accepted as reliable and valid evidence of alcohol-impaired driving, no equivalent technique yet exists that correlates an amount of a drug in the body with the degree of drug-related impairment. To examine this issue, RTI International and the RAND Corporation convened a two-day workshop. The participants discussed the challenges, opportunities, and complexities faced by law enforcement, forensic toxicologists, and prosecutors in their roles collecting, interpreting, and presenting evidence in cases of driving under the influence of drugs. Using these discussions, the panel members identified and ranked needs for law enforcement, forensic toxicologists, and prosecutors to successfully identify and prosecute DUID cases. This report provides the prioritized list of needs and accompanying context from the discussion that resulted from this effort.