Roadblocks or random stops of vehicles are permitted when which condition is met?

Roadblocks or random stops of vehicles are generally considered permissible under the Fourth Amendment when they are based on a neutral standard. This means that the law enforcement agency must apply an objective, predetermined criterion that does not allow for arbitrary decision-making by officers.

Using a neutral standard helps to ensure that all vehicles or drivers are treated equally, minimizing the risk of bias or discrimination in law enforcement practices. For example, if a roadblock is set up to stop every tenth car or based on a specific time interval, it employs a neutral standard that dictates which vehicles are pulled over.

This approach is crucial to maintaining constitutional protections against unreasonable searches and seizures. When roadblocks are conducted with a neutral standard, they are more likely to be upheld in court as being reasonable given the balancing of community safety interests against individual rights.

Other conditions proposed in the options, such as random selection or checking solely for criminal activity, do not ensure the same level of fairness and are more prone to the arbitrary exercise of police discretion, which can lead to constitutional violations. Therefore, a neutral standard is essential for the legality of these vehicle stops.