What is the test for determining whether an area outside a house is protected as curtilage under the Fourth Amendment?

The ultimate question for determining whether an area is protected as curtilage is if the area "is so intimately tied to the home itself" that it should receive the same Fourth Amendment protection as the home. (United States v. Dunn, supra, 480 U.S. at p. 301.) The factors relevant for making this determination are "the proximity of the area claimed to be curtilage to the home, 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." (Ibid.) If the area outside the home is not curtilage, then it is a public area or open field that has no objectionably reasonable expectation of privacy, and the public, including police officers, may lawfully be present. (Id. at pp. 304-305.)