Like all states, Missouri prohibits the operation of a vehicle while under the influence or with a blood alcohol concentration (BAC) of .08% or more. But the BAC limit is only .02% for drivers who are under 21 years old. This article outlines the specifics of a violation as well as the possible penalties.
Missouri doesn't have a specific underage DUI criminal offense like some states. Instead, an offender can be charged criminally for underage consumption and/or lose driving privileges for driving with consumed alcohol.
Underage consumption. A person who's under the age of 21 that is visibly intoxicated or has a BAC of .02% or more can be charged with "minor in possession" (MIP). In other words, a MIP doesn't require possession of an alcohol bottle but can instead be based on the alcohol within the person's body. MIP is a class A misdemeanor and carries up to one year in jail and a maximum $2,000 in fines. The court will also order the driver's license to be suspended, the length of which depends on the number of prior alcohol-related offenses (this suspension runs concurrently with other suspension periods).
License suspension. A driver who's under the age of 21 and is stopped for suspicion of drinking will usually be asked by the officer to submit to a chemical test. If the test result shows a BAC of .02% to .08%, the driver's license will be suspended for 30 days, followed by 60 days with an ignition interlock device (IID). If the offender agrees to install the IID early, it's possible to avoid the 30-day suspension. A second offense will result in a one-year suspension, followed by six months with an IID. Second offenders might be able to obtain a restricted license, which allows limited driving privileges during the suspension period.
BAC of .08% or more. Of course, an underage driver with a BAC of .08% or more can be charged with a standard DUI offense and will face standard DUI penalties.
Missouri's implied consent law generally requires all drivers suspected of underage drinking to submit to an officer's request for a chemical breath or blood test. A test result above .02% will result in the above-mentioned license penalties. But refusal to submit to a chemical test will result in harsher penalties. The unlawful refusal of a chemical test request will result in a one-year license revocation, followed by six months with an IID. This revocation period is in addition to and consecutive to any other license penalties. Restricted licenses are not available for drivers who refused testing.