The short answer is no. There is no set legal limit for the amount of Marijuana (Cannabis) that can be in someone's body.
That being said, there are studies that have measured the blood metabolites that are in someone's body after using cannabis.
A DUI of cannabis is very very hard to prove. Not only do they have to show it was in your blood, they also have to prove that it was there in impairing levels and that because of it, you were unable to drive like a sober person.
You should never admit to using to a police officer even if you are using it legally in California. In fact, other than giving your name and ID (registration and insurance if you are driving as well) you should NEVER talk to the cops. Never perform any Field Sobreity Tests FSTs (unless you are on probation) and never do a chemical test unless you are arrested (or you are under 21).
If you have been arrested for DUI of drugs (including Cannabis) get an experienced DUI lawyer working with you ASAP!! Most of us on AVVO will give you a free consultation.
No there is no particular amount. Note that it stands for driving while impaired ! There is an standard set for impairment, however, it varies for each individual.
There's is almost nothing "specified" about marijuana, especially as it relates to driving. The fact is there is little scientific information about marijuana, its THC concentration, and its effect on driving. (The best information comes from Jan Ramaekers, PhD and Marilyn Huestis, PhD.) My colleagues are correct - there is no per se (e.g. "5ng") limit for driving under the influence of marijuana. There's also no accepted burn-off or metabolization rate for THC.
Simply put - there's just not enough known about marijuana at this time to start setting down numbers, and as such, there's no way to come up with timelines about when to drive and when not to.
Don't drive while impaired. That's about the best we can do at this point.
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