Previous use does NOT equal under the influence. A record of use is not a record of current intoxication. For example: In her life she was drunk once. Therefore, she is drunk?; An example of syllogistic failure 101. All people who are drunk drink alcohol, but not all people who drink alcohol are drunk. We have precision for alcohol. We have a legal chemical that has facilitated the ability for it to be researched. BAC limits are now able to be calibrated to the real-time interaction of the drug on the organism. We do not have the same precision in detecting impairment versus use for most other substances, especially at the level of law enforcement and employment testing scenarios. Isn´t it a scientific embarrassment if the brilliance of advances in precision of detection fail to match precision of the real-life validity of the result for a person being ´detected´? Precision in detection does not equal effect on an individual ´s judgement or effectiveness of policy...Under prohibition, Al Capone´s regime DID equal negative influence, and a century later, records of the period DO show equal negative influence. Scientists; do you really want the precision that you have achieved, and that is worthy of so much pride, to be able to be used so imprecisely to perpetuate unsophisticated policy implementation, victimise citizens, and bolster organised crime?