The often tragic consequences and harsh legal penalties for driving under the influence of alcohol are well publicized. What many people don’t realize is that it is also illegal and punishable in all 50 states to drive under the influence of marijuana (or a combination of alcohol, marijuana, or other drugs).

Laws defining what it means to be “under the influence” of marijuana vary by state, as do applicable punishments.

Any Amount = Under the Influence.  In some states, any amount of marijuana in the driver’s system will conclusively establish that the driver was under the influence.

Above The Threshold = Under the Influence.  In other states a driver who is above a certain blood or urine concentration level will be considered under the influence.

The Defendant’s Behavior or Actions = Under the Influence.  A minority of states require the prosecutor to prove that the driver was under the influence, by pointing to his behavior or driving, regardless of the amount of marijuana in the driver’s system.

States also differ in their definitions of “driving.” For example, in many states, a DUI charge can result from merely sitting in a stationary car while under the influence. Whether this definition of “driving” applies to you depends on the law of the state where you live, and is discussed further below.