What is the Zero Tolerance Law?

Drinking and driving is a serious danger to the public. While the law allows adults to have a limited amount of alcohol in their systems while driving, the fact that those under 21 cannot legally imbibe any alcohol means that they should not have any amount of alcohol in their system while behind the wheel. That's where zero tolerance laws come in. These laws, which are in effect in every state of the nation, ban underage drivers from having even small amounts of alcohol in their system.

Blood alcohol concentration, or BAC, is a measurement of how much alcohol a person has in his system. The biggest factors that influence a person's BAC are their weight, their gender, how much alcohol was consumed and how long ago it was ingested. Generally speaking, a heavier person will have a lower BAC than a lighter person if they drank the same amount of alcohol at the same time, and a man will have a lower BAC than a woman in the same scenario. As time goes on, the BAC will gradually lower as a person metabolizes the alcohol. Of course, each individual's BAC varies based on her own metabolism. Other circumstances that may influence a person's BAC include food consumption, age, how quickly the drink has been consumed and other metabolic factors.

All states have zero tolerance laws, but they are all slightly different. While some states have a strict 0.00 BAC limit for underage drivers, others have a more lenient 0.02 limit, which allows for the use of certain cough syrups, mouthwashes and small amounts of alcohol used for religious functions. No state has a BAC limit above 0.02 percent for those under 21. Even a BAC of 0.02 is still low enough to prevent those under 21 from drinking an alcoholic drink with dinner before driving. Consequences for violating these laws vary by state.

North Carolina is an example of a state with a particularly strict zero tolerance law. Drivers under the age of 21 cannot have a BAC of 0.00 or higher. If a person under 21 has any amount of illegal drugs in her system, she has also violated the zero tolerance law. Penalties include loss of driving privileges for one year, but if the driver was over 18 and it was a first offense, she may be able to get limited driving privileges reinstated by a judge. Drivers under 21 with a BAC over 0.08 percent will face charges as an adult for driving while impaired, but those who have 0.01 to 0.07 percent will face underage DWI charges, which could result in up to 30 days of community service and a $1,000 fine.

California's zero tolerance limit for drivers under 21 is 0.01 percent. Any person under 21 who fails an alcohol screening test or refuses to take the test will lose his license to operate a vehicle for one year and be subject to the standard DUI penalties faced by adult drivers.

New York state set its zero tolerance BAC limit at 0.02 percent with the knowledge that teens may consume trace amounts of alcohol in legal ways through the use of hygiene products or during family and religious rituals. Even so, those under 21 who have a BAC above 0.02 percent or who refuse to take a Breathalyzer test will lose driving privileges for a year. Those with a BAC between 0.05 percent and 0.07 percent may face charges for driving while impaired by alcohol, and those with a BAC of 0.08 percent or above will face adult DWI charges.

Every state has an implied consent law making it illegal for drivers to refuse to take blood alcohol tests, but these laws are much stricter for persons under 21. Whereas adults have the option of refusing a preliminary alcohol screening, or PAS, or a handheld Breathalyzer test, those under 21 must submit to these tests. Refusal to take a Breathalyzer test or a PAS will be considered an automatic failure of the test and subject the person to the specific zero tolerance law penalties in his state.

Read More: How Long do Breathalyzers Detect Alcohol?