Yes. As THC breaks down in the body.... THC may hang around for a long time in fat cells and so forth, but it also creates a bunch of metabolites downstream that may or may not have different time courses. Some things may go away after a couple of hours. In cannabis right now we keep focusing on THC. There are other cannabinoids in marijuana that may have a similar effect. Whether or not those directly relate to impairment.... Perhaps some of those metabolites might give us a good idea as to when the person likely last smoked, which would be very helpful. In addition to having impairment and behavioural measures, you would know that a person smoked roughly three hours ago or something like that.
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