A recent court decision considered a DWI refusal statute in Minnesota, and the court considered whether police officers could obtain a warrant-less urine test. The court held it does not fall within the search incident-to-arrest exception of the Fourth Amendment’s warrant requirement. The intrusion into the motorist’s privacy interest caused by a warrant-less urine test is greater than the government’s need for a urine sample.
When a driver is arrested for impaired driving, is a urine test a valid search incident to arrest (similar to a breath test); or must police delay a demand for a urine test until they obtain a search warrant? 
This matter is now being appealed to the U.S. Supreme Court.
The Prosecutor contended that the warrant-less search of an arrestee’s urine is constitutional under the Fourth Amendment as a search incident to a valid arrest, but when police seek to conduct a search to uncover evidence of criminal wrongdoing reasonableness typically requires police to obtain a judicial warrant before conducting the search.  A neutral and detached magistrate is the gatekeeper and not a police officer engaged in the often competitive enterprise of ferreting out crime. The Prosecutor argued that searching for breath or blood tests of drivers arrested for drunk driving is an established exception to the warrant requirement. The defendant argued that a urine test intrudes upon an individual’s privacy interest that urination is a “natural process” that would occur “sooner or later… even without the test.”
But urine tests can be used to detect and assess a wide range of disorders as to whether an individual is pregnant, diabetic, or epileptic. Urine tests cause considerably more embarrassment than breath tests. There are few activities in our society more personal or private than the passing of urine. Most people describe it by euphemisms if they talk about it at all. It is a function traditionally performed without public observation; indeed its performance in public is generally prohibited by law as well as social custom.  Urinating involves a personal and private bodily function in full view before law enforcement implicates privacy concerns in ways that even a thorough full-body search does not.
The court concluded that police have other measures at their disposal when they have reason to believe that a motorist may be under the influence of alcohol or another substance, availability of alternative forms of testing. Thus, defendant Thompson could not be prosecuted for refusing to submit to an unconstitutional warrant-less blood or urine test and the court held the Minnesota law unconstitutional. 
 Minnesota v. Thompson, 886 NW 2d 224 (MN 2016).
 Birchfield v. North Dakota, (US SC 2016)
 Veronica School District v. Acton, 515 US 646 (1955).
 National Treasury v. VonRaab, 816 F2d 170 (5th Cir. 1987).
 State of Minnesota v. Thompson, (MN SC October 12, 2016).