Arc of 4th Amendment Jurisprudence

Does Fourth Amendment protects people or just places?
What constitutes a “search”? A “seizure”?
Government may not violate a person’s “reasonable expectation of privacy.” What expectation is “reasonable”?
Does Fourth Amendment violation require trespass?
If there is no physical trespass AND no reasonable expectation of privacy, has the Fourth Amendment lost its relevance?

Carpenter v. United States (2018): Mosaic Theory
United States v. Jones (2012): A car is an “effect” within the Fourth Amendment.
Installation and use of the GPS device constituted a “search.”
It was a “physical intrusion.”
It would have been recognized as a “common-law” trespass.
Kyllo v. United States (2001): Where the Government uses a device that is not in general public use, to explore details of a private home that would previously have been unknowable without physical intrusion, the surveillance is a Fourth Amendment "search," and is presumptively unreasonable without a warrant.
California v. Ciraolo (1986): respondant has "knowingly exposed" his backyard to aerial observation, because all that was seen was visible to the naked eye from any aircraft flying overhead.
Katz v. United States (1967): Katz Test:
first that a person have exhibited an actual (subjective) expectation of privacy and,
second, that the expectation be one that society is prepared to recognize as ‘reasonable.’
"What a person knowingly exposes to the public, even in his own home or office, is not a subject of Fourth Amendment protection.
But what he seeks to preserve as private, even in an area accessible to the public, may be constitutionally protected."
Mapp v. Ohio (1967)
Wolf v. Colorado (1949)
Boyd v. United States (1886)