edders23 wrote:
anyway you are never going to accept my arguments about cannabis and I have seen people become disorientated after smoking it so lets leave it at that

Well I don't doubt that, but that wasn't my point. Below is some stuff I was looking at on the rank the other night.
After smoking a joint levels in the blood would be something like 100 micrograms/litre.
The legal limit is 2 micrograms. The driver's level was 2.5 micrograms.
Which it's suggested could easily be attainted simply by passive/accidental inhalation. So watch out the next time someone's smoking pot in your car
Anyway, here's what I drafted the other night - can't be bothered checking the figures again, but the main source of info is via the link at the bottom:
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Passive inhalation of cannabis smoke can result in figures of between 1 and 7 micrograms/litre
One study showed a level of 2 micrograms *nine* days after cannabis use.
An average sized joint could cause a peak concentration of 120 micrograms in just 8 minutes. The legal limit is 2 micrograms.
So the legal limit is 2 micrograms, this guy was measured at 2.5.
Which has been found in tests up to nine days after use, and it's possible that could be exceeded by passive use.
So if he'd recorded 100 micrograms (say) rather than 2.5, I'd say that that was the cause of his impairment.
But at a rough guess I would say the recorded levels wouldn't have been the cause of his visible impairment.
Suspect he'd taken it the day before, or quite a few hours before at least, and that any obvious impairment would have worn off by the time he was stopped.
Another possible reason is maybe that there was a significant delay between him being stopped and being tested. Apparently the level drops rapidly within a few hours, and probably a lot more rapidly than alcohol levels, most obviously. If the test had been conducted another 10-20 minutes or so later he could well have been under the limit.
https://www.drinkdrivingsolicitor.co.uk ... /cannabis/