With a new case for driving while intoxicated (DWI) making its way to the Supreme Court of the United States, it is helpful to review where we are in DWI law to fully understand the implications of the new case, State v. Mitchell.

Much of the newest developments in DWI law have dealt with implied consent laws, and how they have gotten out of hand.

A Quick Review of Implied Consent Laws

Implied consent laws are statutes that penalize the act of refusing to perform a chemical test for your blood alcohol content (BAC), like a breathalyzer or a blood test. These laws imply your consent to a BAC test every time you use your driver's license to drive on the road. Because they are tied to your license, the only penalties that you can face for refusing a BAC test and violating the implied consent law is an automatic license suspension.

However, lawmakers in several states decided that this penalty was too light. They passed laws that made an implied consent violation an actual crime that came with fines and potentially even jail time.

By making it a crime, though, lawmakers inadvertently triggered a suspect's Fourth Amendment rights, leading to the last DWI case that made it to the Supreme Court.

The Supreme Court's Last DWI Case: Birchfield v. North Dakota

Birchfield v. North Dakota involved two drivers in states that criminalized the refusal of a BAC test: One refused a blood test; the other refused a breathalyzer.

Because the Fourth Amendment forbids law enforcement from performing searches or seizures that are “unreasonable” and because police almost never have search warrants for DWI evidence, both BAC tests in Birchfield had to fall into one of the established exceptions to the warrant requirement. Police in Birchfield claimed that the searches they performed – both of which found their suspect's BAC was over the legal limit of 0.08% – were searches incident to arrest.

However, these searches are still “unreasonable” under the Fourth Amendment if they intrude too much into a suspect's reasonable expectations of privacy. This is where the different privacy expectations that someone has with respect to their blood and breath makes a huge difference. Breath tests are not intrusive, carry no medical risks, and do not record information other than BAC. Blood tests, on the other hand, are incredibly intrusive, carry a medical risk of complications or infections, and disclose far more information than just BAC – all the way down to a suspect's DNA.

This is what made the Supreme Court's decision in Birchfield so important for DWI law: The Court deemed the blood test “unreasonable” under the Fourth Amendment and excluded the BAC evidence it found. However, the breath test was permissible.

The case that is currently before the U.S. Supreme Court, State v. Mitchell, is set to build on this distinction and could potentially alter what it means to “consent” to a search for DWI evidence.

DWI Defense Lawyer Doug Murphy Serves Houston Residents

Doug Murphy is a DWI defense lawyer who is closely watching this case. Call his law office in Houston if you have been accused of DWI at (713) 229-8333 or contact him online for help.