Overview of Implied Consent in Drunk Driving Cases

Understandably, when a motorist is pulled over for drunk driving, the motorist is generally reluctant to agree to a chemical test because the test results could be used as evidence to convict the motorist of a drunk driving offense. Many states have implied consent laws that essentially provide that a person that drives a motor vehicle is deemed to have given consent to chemical testing of his or her blood or urine for the purpose of determining the alcohol content of the motorist's blood if the motorist is lawfully arrested.

Implied consent laws encourage motorists to submit willingly to chemical testing by making automatic license suspension the cost of refusing to be tested. In some states, if a motorist refuses to consent to chemical testing, the refusal can be either an offense in and of itself or the basis of an enhanced sentence if the motorist is convicted of the underlying drunk driving offense.

However, before a police officer can request chemical testing, the officer must have probable cause or, depending on the state, at least reasonable grounds to believe that the motorist is under the influence of alcohol. The implied consent laws in some states even require a lawful arrest to occur before a chemical test can be done.

The implied consent statutes have been challenged on the grounds that they violate motorists' constitutional rights. However, multiple courts have held that the statutes do not violate motorists' Fourth Amendment protection from unreasonable search and seizure or motorists' Fifth Amendment right against self-incrimination. The statutes are upheld upon the ground that driving is a privilege subject to reasonable regulation.

Some states with implied consent laws require a police officer to warn a motorist of the possible consequences of refusing to submit to a chemical test. In some states a motorist is given a right to consult an attorney before deciding whether or not to submit to a chemical test. However, because a significant delay could render the tests useless, any right to an attorney before submitting to a chemical test is a limited right. Some states' statutes even require the police officer to notify the motorist of the right to an additional independent chemical test.