It is not a reliable indicator of recent use though, since it can also indicate past use.

I agree we need to set a threshold for impairment. I just want that to be measured reliably so that people who had a brownie last weekend aren't getting in trouble.

Driving isn’t a right. No matter how steeped the US is in car culture, it’s important not to lose sight of this.

Now blood tests show a 12-24 hour window of usage. Much tighter than the 2 to 30 days of other tests. In terms of window of time, that’s essentially good-enough.

Of course anyone who consumes cannabis has a strong desire for a tighter and more accurate test, but you’re really fighting against growing masses of irresponsible users.

If the problem is truly wide-spread like alcohol was (and still is), it’s just a matter of time before states or feds push for a good-enough (for the rest of us) solution.

THC leaves the bloodstream within 24 hours just to be clear.

I know this is a giant hairball and the downvotes and passionate discussion is why I said what I said but in the end, until we have a breathalyzer for THC, it is what it is.