airspace above the curtilage is generally accessible by the public. An area is curtilage if it "harbors the intimate activity associated with the sanctity of a man's home and the privacies of life." Courts make this determination by examining "whether the area is included within an enclosure surrounding the home, the nature of the uses to which the area is put, and the steps taken by the resident to protect the area from observation by people passing by." The Court has acknowledged that a doorbell or knocker is typically treated as an invitation, or license, to the public to approach the front door of the home to deliver mail, sell goods, solicit for charities, etc. This license extends to the police, who have the right to try engaging a home's occupant in a "knock and talk" for the purpose of gathering evidence without a warrant. However, they cannot bring a drug detection dog to sniff at the front door of a home without either a warrant or consent of the homeowner or resident. Exigent circumstance Law enforcement officers may also conduct warrantless searches in several types of exigent circumstances where obtaining a warrant is dangerous or impractical. Under Terry v. Ohio (1968) police are permitted to frisk suspects for weapons. The Court also allowed a search of arrested persons in Weeks v. United States (1914) to preserve evidence that might otherwise be destroyed and to ensure suspects were disarmed. In Carroll v. United States (1925), the Court ruled that law enforcement officers could search a vehicle that they suspected of carrying contraband without a warrant. The Court allowed blood to be drawn without a warrant from drunk-driving suspects in Schmerber v. California (1966) on the grounds that the time to obtain a warrant would allow a suspect's blood alcohol content to reduce, although this was later modified by Missouri v. McNeely (2013). Warden v. Hayden (1967) provided an exception to the warrant requirement if officers were in "hot pursuit" of a suspect. A subset of exigent circumstances is the debated community caretaking exception. Motor vehicle The Supreme Court has held that individuals in automobiles have a reduced expectation of privacy, because (1) vehicles generally do not serve as residences or repositories of personal effects, and (2) vehicles "can be quickly moved out of the locality or jurisdiction in which the warrant must be sought." Vehicles may not be randomly stopped