Last April, in Missouri v. McNeely, the U.S. Supreme Court ruled that drawing blood from someone suspected of driving under the influence without his consent requires a warrant unless there are "exigent circumstances." While the decline in blood alcohol levels over time is one factor in determining whether such circumstances exist, the Court said, that concern by itself does not automatically justify warrantless testing. Citing that decision, a Minnesotan named Wesley Eugene Brooks appealed three convictions for driving while impaired, and the Supreme Court instructed the state courts to reconsider his case in light of McNeely. In all three cases, Brooks supplied a urine or blood sample after he was arrested and instructed that Minnesota's "implied consent" law required him to cooperate, that failure to do so would be a crime, and that he had a right to consult an attorney. Instead of evaluating whether exigent circumstances justified compelling Brooks to provide the samples without a warrant, the Minnesota Supreme Court concluded last week that Brooks was never really compelled. Since he consented to all three searches, the court said, there was no need for a warrant.
Justice David Stras, who thought Brooks' convictions should be upheld based on a "good faith" exception to the exclusionary rule, did not buy the argument that agreeing to a search under the threat of criminal penalties constitutes voluntary consent. "It is hard to imagine how Brooks's consent could have been voluntary when he was advised that refusal to consent to a search is a crime," Stras wrote. He cited a 1976 case in which the Minnesota Supreme Court observed that "the obvious and intended effect of the implied-consent law is to coerce the driver suspected of driving under the influence into 'consenting' to chemical testing, thereby allowing scientific evidence of his blood-alcohol content to be used against him in a subsequent prosecution for that offense." At the time, Stras noted, license revocation was the only penalty for refusing to cooperate with a test. Since then, he said, "Minnesota's implied-consent law has become even more coercive because it now imposes criminal liability for test refusal."
Nonsense, the majority said. After all, Brooks was told he could consult a lawyer, and in all three cases he exercised that right. Never mind that the lawyer's advice seems to have consisted of telling Brooks he had no choice but to cooperate. Since Brooks still could have refused and accepted the legal consequences, the court reasoned, his consent was voluntary. "Consent can be voluntary even if the circumstances of the encounter are uncomfortable for the person being questioned," the court said. "Although refusing the test comes with criminal penalties in Minnesota, the Supreme Court has made clear that while the choice to submit or refuse to take a chemical test 'will not be an easy or pleasant one for a suspect to make,' the criminal process 'often requires suspects and defendants to make difficult choices.'"
Those quotes are from South Dakota v. Neville, a 1983 decision in which the U.S. Supreme Court held that a defendant's refusal to take an alcohol test can be used as evidence against him without violating the Fifth Amendment's ban on compelled self-incrimination—not quite the same as informing an arrestee that he is legally required to submit and will be committing a crime if he doesn't. According to the Minnesota Supreme Court, consent to a search is voluntary even when it is obtained by threat of punishment, as long as the suspect can choose to accept the punishment rather than comply. By the same logic, a suspect who agrees to a search after a cop threatens to beat the crap out of him also has given voluntary consent, because he had the option of taking the beating.
You can read the Minnesota Supreme Court's decision here.