The Fourth Amendment to the U.S. Constitution governs all searches and seizures conducted by government agents. The Amendment contains two separate clauses: a prohibition against unreasonable searches and seizures, and a requirement that probable cause support each warrant issued. The issue of "reasonableness" is generally determined by a balancing test that weighs the degree to which the search intrudes on an individual's legitimate expectation of privacy and the degree to which it is needed for the promotion of legitimate governmental interests, such as crime prevention. In United States v. Katz , the U.S. Supreme Court adopted a two-part test to determine whether a person's expectation of privacy is legitimate. First, the court will determine whether the individual has an actual subjective expectation of privacy. Second, society must be prepared to recognize that expectation as objectively reasonable. The Court has found warrantless searches to be "reasonable" under some circumstances, including those in which consent was given and in which exigent circumstances existed. During the October 2005 term, the Court addressed some of the lingering questions regarding the "reasonableness" of warrantless searches. In Georgia v. Randolph , the Court held that the warrantless search of a defendant's residence based on his wife's consent to the police was unreasonable and invalid as to the defendant, who was physically present and expressly refused to consent. In Brigham City Utah v. Stuart , the Court clarified the appropriate Fourth Amendment standard governing warrantless entry by law enforcement in an emergency situation by holding that police officers may enter a home without a warrant when they have an objectively reasonable basis for believing that an occupant is seriously injured or imminently threatened with such an injury. In Samson v. California , the Court found that a parolee has a reduced expectation of privacy, which fails to outweigh the State's interests in protecting the community. Finally, in United States v. Grubbs , the Court addressed the issue of anticipatory search warrants when it found that an anticipatory search warrant authorizing the search of the defendant's residence on the basis of an affidavit stating that the warrant would be executed upon delivery of a videotape containing child pornography was supported by probable cause. In Katz v. United States , the Supreme Court stated that warrantless searches "are per se unreasonable under the Fourth Amendment subject only to a few specifically established and well-delineated exceptions." One of these exceptions occurs when police obtain voluntary consent of an occupant who shares, or is reasonably believed to share, authority over an area. Generally, anyone who has a reasonable expectation of privacy in the place being searched can consent to a warrantless search, and any person with common authority over, or other sufficient relationship to, the place or effects being searched can give valid consent. The Court has concluded that an individual "assumes a risk" when he or she shares authority over an area. In both United States v. Matlock and Illinois v. Rodriguez , the Court ruled that consent by co-occupants eliminated subsequent Fourth Amendment objections to the admission of seized evidence by an occupant who was not immediately present and therefore did not object at the time to the search. In assessing the "reasonableness" of such searches, the Court looked to the widely shared social expectations, which are generally influenced by property law. However, in Georgia v. Randolph , the Supreme Court found such a search unreasonable as it applies to a physically present occupant who expressly objects to the search. After a domestic dispute, the wife complained to the police that her husband took their son away. When police arrived at the house, she told them that her husband was a cocaine user and there was drug evidence in the home. One officer asked the defendant for permission to search the house, which the defendant expressly refused. That officer then went to the wife for consent to search, which she readily gave. The wife led the officer to an upstairs bedroom, where the officer noticed a drinking straw with a powdery residue, which ultimately proved to be cocaine. The police took the straw to the police station, along with the couple. After getting a search warrant, the police returned to the house and seized further evidence of drug use, which was used to indict the defendant for possession of cocaine. The defendant moved to suppress the evidence as the product of a warrantless search of his house, unauthorized by his wife's consent over his expressed refusal. The trial court denied the motion, ruling that his wife had common authority to consent to the search as established in Matlock . The Georgia appellate court reversed, and the Georgia Supreme Court affirmed, finding that the consent was invalid because, at the time of the warrantless search the defendant was physically present and had clearly refused to consent to the search. The U.S. Supreme Court decided to take the case to resolve a split of authority on whether one occupant may give law enforcement effective consent to search shared premises, as against a co-tenant who is present, but refuses to permit the search. In its 5-3 decision, written by Justice Souter, the Court held that the warrantless search of a defendant's residence based on his wife's consent to the police was unreasonable as to a physically present defendant who expressly refused to consent. The Court built on its previous decision in Minnesota v. Olson , wherein it found that overnight houseguests have a legitimate expectation of privacy in their temporary quarters. The Court concluded that if, as was found in Olson , the "customary expectation of courtesy or deference is a foundation of Fourth Amendment rights of a houseguest," it should follow that a co-inhabitant should have even a stronger claim. The Court found that there is no societal or common understanding that one co-tenant generally has a right or authority to prevail over the express wishes of another. In reaching its decision, the Court noted that there were alternatives available to bring the criminal activity to light. For example, the co-tenant could bring evidence to the police on her own initiative. Or, exigent circumstances could justify immediate action on the police's part, if the objecting tenant cannot be incapacitated from destroying easily disposable evidence during the time required to get a warrant. The majority distinguished Randolph from Matlock/Rodriguez based on the fact that in Randolph the defendant expressly denied consent to search, whereas in Matlock/Rodriguez the defendants were silent. The Court stated: "In sum, there is no common understanding that one co-tenant generally has a right or authority to prevail over the express wishes of another, whether the issue is the color of the curtains or invitations to outsiders." The Court acknowledged that the line drawn between Matlock and Illinois v. Rodriguez , where the defendants in both cases were nearby but simply not asked for their permission, and Randolph was a fine one. Nevertheless, the Court refused to require police who have obtained consent from one resident to take "affirmative steps" to find out whether another resident objects. Instead, the Court adopted a simpler rule that "a physically present inhabitant's express refusal of consent to a police search is dispositive as to him, regardless of the consent of a fellow occupant." In a dissenting opinion, Chief Justice Roberts, joined by Justice Scalia, criticized the Court's reliance on its understanding of social expectations and argued that a straightforward application of Matlock ' s "assumption-of-the-risk" principle should allow police to rely on one resident's consent over another resident's objection. The dissenters argued that the majority ruling "provides protection on a random and happenstance basis," which may protect the occupant at the door, but not one "napping or watching television in the next room." It is a general rule that searches and seizures inside a home without a warrant are presumptively unreasonable for Fourth Amendment purposes. However, this search warrant requirement is subject to certain exceptions, such as in cases where the exigencies of the situation make the needs of the law enforcement so compelling that a warrantless search is objectively reasonable under the Fourth Amendment. The Supreme Court addressed such a circumstance in Brigham City v. Stuart where, in reversing the Utah Supreme Court's decision, the Court held that police may enter a home without a warrant when they have an objectively reasonable basis for believing that an occupant is seriously injured or imminently threatened with such injury. This case arose when police officers responded to a call regarding a loud party at a residence. Upon arriving on the scene, the officers observed two juveniles drinking beer in the backyard. They entered the backyard, looked into the window and saw an altercation taking place in the kitchen. The officers testified that they saw four adults attempting to restrain a juvenile, and that the juvenile struck one of the adults, who was then spitting blood. The officers announced their presence and the altercation ceased. The officers subsequently arrested each of the adults for contributing to the delinquency of a minor, disorderly conduct, and intoxication. The adults argued that the warrantless entry violated the Fourth Amendment, and the Utah courts agreed. Writing for a unanimous Court, Chief Justice Roberts noted that one exigency obviating the warrant requirement is the need to assist individuals who are seriously injured or threatened with such injury. The petitioners did not take issue with this principle, but instead advanced two reasons why the officers' entry was unreasonable. First, they argued that the officers were more interested in making arrests than quelling violence. The Court noted that the officers' subjective motivation was irrelevant. Relying on the Court's previous ruling in Welsh v. Wisconsin , the petitioners further contended that their conduct was not serious enough to justify the warrantless intrusion. Distinguishing the facts in Welsh , the Court responded that the officers were confronted by ongoing violence occurring within the home, as opposed to a mere potential emergency, such as the need to preserve evidence. The Court concluded that the officers' entry to the home was reasonable under the totality of the circumstances. Given the tumult at the house upon their arrival, it was obvious that a knock on the front door would have been futile.