Sobriety checkpoints are legal in Maryland (see 479 A.2d 903 (Md. 1984)). These checkpoints (also referred to as "mobile checkpoints" or "roadblocks") are police traffic stops that are not tied to any specific or individual suspicions. The locations chosen for checkpoints are temporary and "random" (although you may be able to learn more about when or where these checkpoints will be instituted in Maryland by checking roadblock.org or duiblock.com).
During a sobriety checkpoint, drivers are briefly detained and interviewed after which suspicious drivers are subject to sobriety tests. The goal of these checkpoints is to weed out inebriated drivers and therefore keep the roads safer. According to the Center for Disease Control and Prevention (CDC), sobriety checkpoints have the potential to prevent nearly 1 out of 10 DUI-related deaths.
Yes, the Constitution requires that a police officer have probable cause for a traffic stop. But the U.S. Supreme Court has ruled that the dangers from drunk driving outweigh the "degree of intrusion" of sobriety checkpoints and they are an exception to the search and seizure provisions of the U.S. Constitution. Subsequently the National Highway Safety Transportation Board has issued guidelines for police when administering a sobriety checkpoint. Perhaps the most important guideline is that the police must publicize the checkpoints ahead of time. Each state may also impose its own guidelines (or the states may outlaw checkpoints entirely, as 12 states have done).
Learn more about Maryland’s DUI laws.