Sobriety checkpoints or roadblocks involve law enforcement officials stopping every vehicle (or more typically, every nth vehicle) on a public roadway and investigating the possibility that the driver might be too impaired to drive. They are often set up late at night or in the very early morning hours and on weekends, at which time the proportion of impaired drivers tends to be the highest.
With a portable and quick alcohol breath test, the police can test all drivers (if the law permits), and process the cars one by one as in a conveyor belt. When there is no quick test, a more complicated routine is necessary. Upon suspicion, the stopped driver is required to exit the vehicle and take a roadside sobriety test that requires the demonstration of both mental and balance skills. If the officer determines that the test has not been passed, the driver is then required to take an alcohol breath test (referred to as a Breathalyzer test in the United States).
At a sobriety checkpoint, drivers are necessarily stopped without reasonable suspicion, and may be tested summarily and without probable cause. Jurisdictions that allow sobriety checkpoints often carve out specific exceptions to their normal civil protections, in order to allow sobriety checkpoints.
Driving under the Influence of alcohol is a special type of crime, as driving with a blood alcohol content (BAC) over a set limit is defined as the crime; it is not necessary to drive recklessly or cause an accident in order to be convicted. To determine BAC accurately, it is generally necessary for the driver to subject themselves to tests that are self incriminating, and drivers sometimes exercise their right against self incrimination to refuse these tests. To discourage this, some jurisdictions set the legal penalties for refusing a BAC test to equal or worse than those for a failing a BAC test. In other jurisdictions, the legal system may consider refusing the roadside alcohol breath test to be probable cause, allowing police to arrest the driver and conduct an involuntary BAC test.
The Fourth Amendment to the United States Constitution states that: “The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.” Thus the Constitution would appear to prohibit people from being stopped without a search warrant or at least without probable cause that they have committed a crime; however, the warrant requirement only attaches should the search be unreasonable and the Supreme Court, as shown below, decided that such stops are not unreasonable under certain circumstances.
The Michigan Supreme Court had found sobriety roadblocks to be a violation of the Fourth Amendment. However, by a 6-3 decision in Michigan Dept. of State Police v. Sitz (1990), the United States Supreme Court found properly conducted sobriety checkpoints to be constitutional. Although acknowledging that such checkpoints infringed on a constitutional right, Chief Justice Rehnquist argued that the state interest in reducing drunk driving outweighed this minor infringement.
Dissenting justices argued that the Constitution doesn’t provide exceptions. "That stopping every car might make it easier to prevent drunken driving...is an insufficient justification for abandoning the requirement of individualized suspicion", dissenting Justice Brennan insisted.
Chief Justice Rehnquist argued that an exception was justified because sobriety roadblocks were effective and necessary. On the other hand, dissenting Justice Stevens countered that "the findings of the trial court, based on an extensive record and affirmed by the Michigan Court of Appeals, indicate that the net effect of sobriety checkpoints on traffic safety is infinitesimal and possibly negative." And even if roadblocks were effective, the fact that they work wouldn’t justify violating individuals’ constitutional rights, some justices argued.
Although the U.S. Supreme Court has found sobriety checkpoints to be constitutionally permissible, eleven states have found that sobriety roadblocks violate their own state constitutions or have outlawed them. Opposition to sobriety roadblocks is generally stronger among civil libertarians, conservatives and libertarians.
In approving "properly conducted" checkpoints, Chief Justice Rehnquist implicitly acknowledged that there must be guidelines in order to avoid becoming overly intrusive. In other words, checkpoints cannot simply be set up when, where and how police officers choose. As often happens in Supreme Court decisions, however, the Chief Justice left it to the states to determine what those minimal safeguards must be, presumably to be reviewed by the courts on a case-by-case basis.
In an effort to provide standards for use by the states, the National Highway Traffic Safety Administration subsequently issued a report that reviewed recommended checkpoint procedures in keeping with federal and state legal decisions. ("The Use of Sobriety Checkpoints for Impaired Driving Enforcement", DOT HS-807-656, Nov. 1990) An additional source of guidelines can be found in an earlier decision by the California Supreme Court (Ingersoll v. Palmer (43 Cal.3d 1321 (1987)) wherein the Court set forth what it felt to be necessary standards in planning and administering a sobriety checkpoint:* Decision making must be at a supervisory level, rather than by officers in the field.
The Centers for Disease Control, in a 2002 Traffic Injury Prevention report, found that in general, the number of alcohol related crashes was reduced by 20% in states that implement sobriety checkpoints compared to those that do not.