Comedy sketch imagines a sobriety test for stoners

boing
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HAHAHAHAHAHAHA

But let’s talk about the problem of per se DUI laws for pot.

Why do per se laws work for alcohol, but not for cannabis? The primary reason is that alcohol and cannabis are different drugs, with different effects and metabolism. Alcohol is water-soluble and diffuses rapidly throughout the body, with peak effects and impairment coming around one hour after ingestion and slowly dissipating in tandem with the blood-alcohol level over hours. At any point in this pathway, the blood-alcohol level can be measured and will reliably predict driving impairment.

Cannabis behaves very differently in the body, for a variety of reasons.

  1. THC is poorly soluble in blood, so it is taken up into the body’s fat stores rapidly. Maximum body THC levels occur around ten minutes after smoking, and one study showed that blood levels were down below 5 ug/L at 1.4 hours and below 2 at 3.3 hours (this was on average; some people remained above 2 for more than eight hours).
  2. Because THC can build up in fat cells and be subsequently released over a long time period, some people can still have THC in their blood from past exposure, with no discernible impairment. In the study quoted above, one participant had a positive THC level of 4.9-6.3 ug/L after overnight abstention on six different occasions. This person, along with many medical cannabis users, would be unable to ever drive legally, due to prolonged THC excretion, despite no evidence of impairment.
    3.By the time a blood level is drawn, there may be very little THC left in the blood. Impairment can last longer than three hours, yet most will be below the per se limit by that time. Due to individual variability and the rapid decline in THC levels, it is impossible to calculate the level of THC at the time of the accident based on a later blood level.
    4.A number of studies have found that it is not possible to link a random measurement of blood THC to impairment levels, as impairment can take place below 2 ng/mL. Equally, people with a level of THC in their blood of > 5 ng/mL can demonstrate no impairment. Wide variations in level of impairment are seen in different individuals with the same blood THC level.
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