Here's probably more information than you wanted. There are different types of checkpoints. Permanent checkpoints are allowed in areas where there is a lower expectation of privacy. The best example of this is close to the international border. If a checkpoint is set up by the border, then the justification is that it is part of the “extended” border (you have very little privacy rights at a border but this type of checkpoint generally has to be within 100 miles of the border). However, if a permanent checkpoint is set up by the border, it’s scope is limited to its purpose. That means, that if it is an immigration checkpoint, then the agents have to let you go once they have ascertained that you are not undocumented or that you are not involved in alien-smuggling activity. If they don’t have any reason to believe that you have violated the immigration laws then, they have to let you go, even if you refuse to open your trunk or let them make a more thorough search. For a good discussion on this check out the Ninth Circuit’s decision in United States v. Martinez-Fuertes, 414 F.2d 305 (9th Cir. 1975)
A temporary checkpoint is a different thing. In Indianapolis v.Edmond, 512 U.S. 32, the Supreme Court held that the police can’t make random stops at a checkpoint without “individualized suspicion.” That is to say, police can’t just set up a checkpoint to see if anyone is breaking the law, in general. In 2004, however, the Supreme Court limited Edmond in a case called Illinios v. Lidster. In that case, the police created a checkpoint to find out information about a hit and run accident, stopped the cars very briefly and asked them about the accident. The Supreme Court reasoned that these types of checkpoints were okay because they were meant to gather information rather than to investigate the passengers for law violations. They were investigating a crime in particular (the hit and run) and not the passengers in the car. Also check out Michigan Dept of State Police v. Sitz, 496 U.S. 444. That’s were the Supreme Court says that sobriety checkpoints are okay. The justification is that there is an immediate danger to the public if there are drunk drivers on the road. So, because drunk driving and traffic safety go hand-in-hand then sobriety checkpoints are okay.
Hope this helps!
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