The three standard types of field sobriety tests that law enforcement uses aren't reliable to test for marijuana. They include the horizontal gaze nystagmus test, the walk and turn, and the one-leg stand. In the first test, the twitching that is present in your peripheral vision that is always present in the case of alcohol impairment doesn't apply to marijuana. Further, testing for balance and stability, like in the second and third tests, aren't reliable for marijuana either. If you've been charged with a DWI due to marijuana impairment, make sure your attorney is well-versed in the science.