Here in the united states francis would never be allowed to drive again. It is illegal to operate a motor vehicle with any of your medications that you are on.

Why a Pot 'Breathalyzer' Won't Work

The problem is that recent research clearly shows that the levels of marijuana's active compound, called tetrahydrocannabinol or THC, don't line up in a straightforward way with how impaired people are, according to the paper, published today (Jan. 25) in the journal Trends in Molecular Medicine.

Researchers also need to figure out how long it takes for the body to break down certain compounds called cannabinoids, and flush them out of the system.

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