Client stopped for speeding. Officer detects odor of fresh burnt marijuana, blood shot eyes and odor of alcohol. Client admits to smoking half a joint just prior to stop but completes field sobriety tests without difficulty. Defense cross exam establishes standard field sobriety tests are not validated for detection of impairment by marijuana. Blood test is negative for alcohol but positive for marijuana. State’s expert witness admits that positive blood tests for THC only establish “window of use” and do not establish impairment which can vary significantly among individual marijuana users. Not guilty verdict following trial.