The Constitution of the United States pretty clearly says that police can’t just stop someone and conduct an investigation unless there are “articulable facts” indicating possible criminal activity….So how can they do exactly that with DUI roadblocks?
Good question. And it was raised in the case of Michigan v. Sitz (496 U.S. 444), in which the U.S. Supreme Court reviewed a decision of the Michigan Supreme Court striking down drunk driving roadblocks as unconstitutional. In a 6-3 decision, the Court reversed the Michigan court, holding that roadblocks were constitutionally permissible.
Chief Justice Rehnquist began his majority opinion by admitting that DUI roadblocks (aka “DUI sobriety checkpoints”) do, in fact, constitute a “seizure” within the language of the 4th Amendment. In other words, yes, it’s a blatant violation of the Constitution. However….
However, it’s only a "minor violation", and there’s all this “carnage” on the highways MADD tells us we’ve got to do something about. The “minimal intrusion on individual liberties”, Rehnquist wrote, must be “weighed” against the need for and effectiveness of roadblocks. In other words, the ends justify the (illegal) means….aka, “The DUI Exception to the Constitution”.
The dissenting justices pointed out that the Constitution doesn’t make exceptions: The sole question is whether the police had probable cause to stop the individual driver. As Justice Brennan wrote,
“That stopping every car might make it easier to prevent drunken driving…is an insufficient justification for abandoning the requirement of individualized suspicion….The most disturbing aspect of the Court’s decision today is that it appears to give no weight to the citizen’s interest in freedom from suspicionless investigatory seizures”.
Rehnquist’s justification for ignoring the Constitution rested on the assumption that DUI roadblocks were “necessary” and “effective”. Are they? As Justice Stevens wrote in his own dissenting opinion, the Michigan court had already reviewed the statistics on DUI sobriety checkpoints/roadblocks:
“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”.
p.s. The case was sent back to the Michigan Supreme Court to change its previous decision accordingly. But the Michigan Supreme Court sidestepped Rehnquist by holding that DUI checkpoints, if now permissible under the U.S. Constitution, were not permissible under the Michigan State Constitution! The Court ruled again in favor of the defendant — in effect saying to Rehnquist, “If you won’t protect our citizens, we will”.