AMENDMENT IV: "The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized." 
Justice Louis Brandeis stated that the Fourth Amendment sets forth "the right to be left alone - the most comprehensive of rights and the right most valued by civilized men." James Otis, a lawyer in colonial Massachusetts and an early patriot, opined, "A man's house is his castle; whilst he is quiet, he is as well guarded as a prince in his castle."
Evolving jurisprudence and technological progress have caused many to question whether the thick, stone walls of the castle have become paper thin, however. And while Katz v. United States (1967) held that the Fourth Amendment protects people, not places, much law has been established promoting the legal theory that, once you venture outside of your castle, your right to privacy is even more diminished. Consider your rights with respect to having to identify yourself at the request of law enforcement; stopping at checkpoints; going through airport security; implied consent to drug and alcohol testing as a privilege of driving; student searches, etc.
This evolution has to be considered vis-a-vis our changing society. While the evolution has sinister applications - and implications - these changes also beg questions about balancing freedom with safety. Can a law enforcement officer do his duty if he sees a person walking away from the scene of a crime, yet cannot inquire of the person's identity? Don't implied consent statutes render the unreasonableness of a sobriety checkpoint moot? Doesn't terrorism make airport security searches, on balance, a necessary evil? And tragedies like Columbine, the necessity for student searches at schools?
Know your rights. If you have questions, contact an attorney.
John C. Kaspar, Esq., Gray and Duning, (513) 932-2871