because the officer does not have articulable and reasonable suspicion that a motorist is unlicensed or that an automobile is not registered, or either the vehicle or an occupant is otherwise subject to seizure for violation of law. Where society's need is great, no other effective means of meeting the need is available, and intrusion on people's privacy is minimal, certain discretionless checkpoints toward that end may briefly detain motorists. In United States v. Martinez-Fuerte (1976), the Supreme Court allowed discretionless immigration checkpoints. In Michigan Dept. of State Police v. Sitz (1990), the Supreme Court allowed discretionless sobriety checkpoints. In Illinois v. Lidster (2004), the Supreme Court allowed focused informational checkpoints. However, in City of Indianapolis v. Edmond (2000), the Supreme Court ruled that discretionary checkpoints or general crime-fighting checkpoints are not allowed. Warrant Under the Fourth Amendment, law enforcement must receive written permission from a court of law, or otherwise qualified magistrate, to lawfully search and seize evidence while investigating criminal activity. A court grants permission by issuing a writ known as a warrant. A search or seizure is generally unreasonable and unconstitutional if conducted without a valid warrant and the police must obtain a warrant whenever practicable. Searches and seizures without a warrant are not considered unreasonable if one of the specifically established and well-delineated exceptions to the warrant requirement applies. These exceptions apply "[o]nly in those exceptional circumstances in which special needs, beyond the normal need for law enforcement, make the warrant and probable cause requirement impracticable." In these situations where the warrant requirement doesn't apply a search or seizure nonetheless must be justified by some individualized suspicion of wrongdoing. However, the U.S. Supreme Court carved out an exception to the requirement of individualized suspicion. It ruled that, "In limited circumstances, where the privacy interests implicated by the search are minimal and where an important governmental interest furthered by the intrusion would be placed in jeopardy by a requirement of individualized suspicion" a search [or seizure] would still be reasonable. Probable cause The standards of probable cause differ for an arrest and a search. The government has probable cause to make an arrest when "the facts and circumstances within their knowledge and of which they had reasonably trustworthy information" would lead a prudent person to believe the arrested person had committed or was committing a crime. Probable cause to arrest must exist before the arrest is made.