The Fourth Amendment says, '[t]he 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.'
A seizure occurs when the government takes possession of items or detains people.
A search is any intrusion by the government into something in which one has a reasonable expectation of privacy.
Some examples of searches include: reaching into your pockets or searching through your purse; entering into your house, apartment, office, hotel room, or mobile home; and examining the contents of your backpack or luggage. Depending on the facts, eavesdropping on your conversations or wiretapping of your communications can also constitute a search and seizure under the Fourth Amendment.
The Fourth Amendment requires searches and seizures to be 'reasonable', which generally means that police must get a search warrant if they want to conduct a legal search or seizure, although there are exceptions to this general rule. If a search or seizure is 'unreasonable' and thus illegal, then police cannot use the evidence obtained through that search or seizure in a criminal trial. This is called the exclusionary rule and it is the primary incentive against government agents violating your Fourth Amendment rights.
The Fourth Amendment protects you from unreasonable searches whether or not you are a citizen. In particular, the exclusionary rule applies to all criminal defendants, including non-citizens. However, the exclusionary rule does not apply in immigration hearings, meaning that the government may introduce evidence from an illegal search or seizure in those proceedings.
The Fourth Amendment applies whenever the government — whether local, state or federal — conducts a search or seizure. It protects you from an unreasonable search or seizure by any government official or agent, not just the police.
The Fourth Amendment does not protect you from privacy invasions by people other than the government, even if they later hand over what they found to the government — unless the government directed them to search your things in the first place.
Your Fourth Amendment rights against unreasonable searches and seizures cannot be suspended — even during a state of emergency or wartime — and they have not been suspended by the USA PATRIOT Act or any other post-9/11 legislation.
If you are ever searched or served with any kind of government order, contact a lawyer immediately to discuss your rights. Contact a lawyer any time you are searched, threatened with a search, or served with any kind of legal papers from the government or anyone else. If you do not have a lawyer, pro bono legal organizations such as EFF are available to help you or assist in finding other lawyers who will.
The Fourth Amendment only protects you against searches that violate your reasonable expectation of privacy. A reasonable expectation of privacy exists if 1) you actually expect privacy, and 2) your expectation is one that society as a whole would think is legitimate.
This rule comes from a decision by the United States Supreme Court in 1967. Katz v. United States, holding that when a person enters a telephone booth, shuts the door, and makes a call, the government can not record what that person says on the phone without a warrant. Even though the recording device was stuck to the outside of the phone booth glass and did not physically invade Katz’s private space, the Supreme Court decided that when Katz shut the phone booth’s door, he justifiably expected that no one would hear his conversation, and that it was this expectation — rather than the inside of the phone booth itself — that was protected from government intrusion by the Fourth Amendment. This idea is generally phrased as 'the Fourth Amendment protects people, not places.'
A big question in determining whether your expectation of privacy is 'reasonable' and protected by the Fourth Amendment arises when you have 'knowingly exposed' something to another person or to the public at large. Although Katz did have a reasonable expectation of privacy in the sound of his conversation, would he have had a reasonable expectation of privacy in his appearance or actions while inside the glass phone booth? Probably not.
Thus, some Supreme Court cases have held that you have no reasonable expectation of privacy in information you have 'knowingly exposed' to a third party — for example, bank records or records of telephone numbers you have dialed — even if you intended for that third party to keep the information secret. In other words, by engaging in transactions with your bank or communicating phone numbers to your phone company for the purpose of connecting a call, you’ve 'assumed the risk' that they will share that information with the government.
You may 'knowingly expose' a lot more than you really know or intend. Most information a third party collects — such as your insurance records, credit records, bank records, travel records, library records, phone records and even the records your grocery store keeps when you use your 'loyalty' card to get discounts — was given freely to them by you, and is probably not protected by the Fourth Amendment under current law. There may be privacy statutes that protect against the sharing of information about you — some communications records receive special legal protection, for example — but there is likely no constitutional protection, and it is often very easy for the government to get a hold of these third party records without your ever being notified.
Here are some more details on how the Fourth Amendment will — or won't — protect you in certain circumstances:
Residences. Everyone has a reasonable expectation of privacy in their home. This is not just a house as it says in the Fourth Amendment, but anywhere you live, be it an apartment, a hotel or motel room, or a mobile home.
However, even things in your home might be knowingly exposed to the public and lose their Fourth Amendment protection. For example, you have no reasonable expectation of privacy in conversations or other sounds inside your home that a person outside could hear, or odors that a passerby could smell (although the Supreme Court has held that more invasive technological means of obtaining information about the inside of your home, like thermal imaging technology to detect heat sources, is a Fourth Amendment search requiring a warrant). Similarly, if you open your house to the public for a party, a political meeting, or some other public event, police officers could walk in posing as guests and look at or listen to whatever any of the other guests could, without having to get a warrant.
Business premises. You have a reasonable expectation of privacy in your office, so long as it’s not open to the public. But if there is a part of your office where the public is allowed, like a reception area in the front, and if a police officer enters that part of the office as any other member of the public is allowed to, it is not a search for the officer to look at objects in plain view or listen to conversations there. That’s because you’ve knowingly exposed that part of your office to the public. However, if the officer does not stay in that portion of the premises that is open to the public — if he starts opening file cabinets or tries to go to private offices in the back without an invitation — then his conduct becomes a search requiring a search warrant.
Trash. The things you leave outside your home at the edge of your property are unprotected by the Fourth Amendment. For example, once you carry your trash out of your house or office and put it on the curb or in the dumpster for collection, you have given up any expectation of privacy in the contents of that trash. You should always keep this in mind when you are disposing of sensitive documents or anything else that you want to keep private. You may want to shred all paper documents and destroy all electronic media. You could also try to put the trash out (or unlock your trashcan) right before it’s picked up, rather than leaving it out overnight without a lock.
Public places. It may sound obvious, but you have little to no privacy when you are in public. When you are in a public place — whether walking down the sidewalk, shopping in a store, sitting in a restaurant or in the park — your actions, movements, and conversations are knowingly exposed to the public. That means the police can follow you around in public and observe your activities, see what you are carrying or to whom you are talking, sit next to you or behind you and listen to your conversations — all without a warrant. You cannot necessarily expect Fourth Amendment protection when you’re in a public place, even if you think you are alone. Fourth Amendment challenges have been unsuccessfully brought against police officers using monitoring beepers to track a suspect’s location in a public place, but it is unclear how those cases might apply to more pervasive remote
