.08 refers to the amount of alcohol in a person's system. It is commonly referred to as the legal limit. Alcohol is not illegal, so it is not illegal to drink some alcohol and drive. What IS illegal is to drink an amount that impairs your driving ability, or puts you over the legal limit. Marijuana, on the other hand, is illegal in all but a few instances (medical marijuana). As a result, driving with ANY amount of marijuana is illegal. Most ethical crime lab "scientists" will admit that the amount of marijuana reflected in a blood test shows only recent or habitual use, not a level of impairment. The other way the police will attempt to measure the level of impairment from marijuana is through field sobriety tests performed by a drug recognition expert (DRE). These tests, however, are not valid scientifically and readily discredited by an experienced DUI defense lawyer.
Marijuana has active and non-active ingredients that can be measured in blood and urine. Unlike alcohol, there is no agreement as to the amount where driving impairment can be presuemd (in most states)
Every case varies depending on the law and the facts. Because questions often fail to disclose important facts, these 'answers' cannot and should not be relied upon as a replacement for a full or complete review of an actual case by a retained attorney. It is axiomatic that one only 'gets what they pay for', and this is one of those situations where such a phrase generally applies.