In DUI cases police routinely order people to take breath tests. For years no one gave much thought to whether such orders are legal. The 2013 case of Missouri v. McNeely may be changing that situation.
In McNeely the Supreme Court held that a warrant was required before a blood test could be taken against a person’s will. The argument went that sticking a needle into someone’s arm and taking their blood to analyze it invades a person’s privacy. Protecting personal privacy from government intrusion is the purpose of the Fourth Amendment. That amendment says that individuals are protected from government intrusion “in their persons, houses, papers and effects” from unreasonable searches.
As a general rule a search is unreasonable unless the police first obtain a warrant for that search. The warrant must be based upon probable cause to believe the search will turn up evidence of criminal activity. A warrant is in order from a judge or magistrate that says there is enough evidence to believe a search will produce evidence of a crime, and therefore a search is allowed. When police search without a warrant it is presumed to be an unreasonable search unless it fits into a recognized exception to the warrant requirement.