Unless you grab the wheel from the passenger seat like Jordyn Beebe in my post “Passenger Gets Valentine’s Day DUI” a passenger cannot get charged with a DUI if they are not driving the vehicle. California law requires that the defendant drive the vehicle. It is not unheard of, however, if drunk passengers during a DUI arrest get charged with drunk in public. While it may be charged, it is often fought by attorneys in court because the prosecutor needs to prove that, amongst other things, the passenger was in a public place and was unable to exercise care for their safety or for the safety of others. This is often difficult for the prosecutor to prove.
What about checkpoints? Passengers have the same rights as drivers at checkpoints. As several of my prior posts point out, officers can only briefly screen drivers and request their licenses to determine whether or not they are impaired and if they hold a valid license. If a driver does not seem under the influence and they hold a valid license, they must be allowed to pass. After it is determined that the driver is not impaired and they hold a valid license, officers must have probable cause to believe that the passenger has committed a crime in order to investigating the passenger. Otherwise, they too must be allowed to go.
Probable cause can be found in a number of ways. For example, if the officer sees drugs, in plain sight, with the passenger during the stop of the driver at the checkpoint, they can begin investigating the passenger. Even then, passengers have the same rights as a driver. They have a right to remain silent and the right to an attorney. And both should be invoked immediately after an investigation commences. Since they are not the driver, passengers do not have to submit to a chemical test under the implied consent laws. Remember, it is not illegal to be a drunken passenger in a vehicle. In fact, it is in encouraged over driving themselves when the driver is sober.