Yesterday, the U.S. Supreme Court ruled that while the Fourth Amendment permits warrentless breath tests, it does not permit warrentless blood tests.

In its opinion, the court said breath tests do not “implicate significant privacy concerns;  The physical intrusion is almost neglegible, while blood tests “require piercing the body and thus are significantly more intrusive than blowing into a tube.  A blood test also gives law enforcement a sample that can be preserved and from which it is possible to extract information beyond a simple BAC reading.

The court said the states involved in the case hadn’t shown any “satisfactory justification for demanding the more intrusive alternative (of a blood test) without a warrant” given that the less intrusive alternative of a breath test is available.

It added motorists can’t be criminally punished for refusing to submit to a blood test based on legally implied consent to submit to them.  “It is one thing to approve implied consent laws that impose civil penalties . . . but quite another to insist upon an intrusive blood test and then impose criminal penalties on refusal to submit.”

The case is Birchfield v. North Dakota, No. 14-1468, decided June 23, 2016.