still with us from seattle, alison holcomb criminal director of the civil liberties union and jonathanfessor at the georgia washington law school and we have professor of public policy at carnegie mellen university. what happens when now there is another substance you have to worry about people using and then driving and part of the challenge being that there is no test that says reliable as let's say a breathalyzer for alcohol when it comes to thc in the system and trying to understand how long someone remains impaired after smoking. >> we do have a learning curve here when it comes to the impact of thc on driving. we do have some preliminary studies that suggest some guidelines for standards and those were the studies we looked at when we established a per se standard for active thc. when i talk about active thc it's important for a lot of people to understand that there is active thc that causes impairment and separately the inactive metabolize that shows up in workplace tests for example. our drug standard in washington does not apply to that inactive standard but only to the activ