Too High to Drive?

Posted Thursday, February 27, 2014 by Andrew Charles Huff

Washington recently legalized the personal use of marijuana for those age 21 and over by way of Initiative 602, joining the state of Colorado. This new law has similar restrictions to the use of alcohol. For example, besides being a certain age, one cannot simply enjoy a toke out in public (at least not legally, that is). And like alcohol, driving a vehicle while affected by marijuana is illegal.

But how does the law determine if you have taken too many hits off the bong? The first way is if you have a measured amount of 5.0 ng of THC concentration in your blood within two hours of driving a vehicle. This is normally measured by drawing a sample of your blood and having it analyzed. The other method is based primarily upon observations made by the police officer, including the use of field sobriety tests, of which many we have all heard of, such as the One Leg Stand, and Walk and Turn.

One challenge facing officers investigating a driver suspected of being impaired by marijuana alone are the use of these standardized field sobriety tests, such as the Walk and Turn, and One Leg Stand. The problem is these tests were solely developed to use on drivers suspected of “alcohol” impairment, not marijuana. The various studies which developed this battery of tests for law enforcement concluded that those who display a specific number of clues were likely to be over a .10 blood alcohol level. No where was it determined or even mentioned that these tests could be used for those suspected of being too “high” to drive.

So the question remains that unless there is an admissible blood draw showing 5.0 ng of THC, just what is “too high to drive?”