California DUI law makes it illegal to drive under the influence of marijuana. However, a skilled lawyer often has an easier task defending marijuana-related DUI cases than cases where alcohol is involved.
In drunk driving prosecution, the defendant is presumptively guilty when the blood alcohol level is 0.08 percent or more. By contrast, there is no set legal threshold for when a person is presumptively impaired when using marijuana. This lack of a bright line standard makes it more difficult for the prosecution to prove their case.
In addition, a knowledgeable attorney can often defend these cases successfully by relying on experts and various studies showing lack of scientific agreement on when marijuana causes impairment. Scientific and expert literature on the subject contains data that there is no impairment if the ingestion occurred more than two to three hours before driving.