Searches And Seizures
Your constitutional protection against an illegal search or seizure is actually a protection of your right to privacy against unauthorized intrusion by the government. Thus, search and seizure questions must be framed in the context of personal privacy rights that are particular to each case.
In order to investigate criminal activity, law enforcement officers and government agents often "search and seize" people, their homes and belongings. However, such investigations must adhere to strict constitutional constraints, or the searches and seizures will be found by the courts to be unreasonable and illegal. The Fourth Amendment of the United States Constitution protects citizens against unreasonable searches and seizures where there is an "expectation of privacy." It also provides the requirements for searches and seizures, including the issuance of warrants based on probable cause.
Since your right to privacy is not absolute and only extends to certain areas (home, car or office, for example), a search or seizure is not always unreasonable in itself. For instance, a search and/or seizure is reasonable where there is probable cause to suspect criminal activity. In these cases, warrants are usually obtained from a judge and a search proceeds without violating constitutional rights. Searches and seizures without warrants are also reasonable where special, or "exigent" circumstances exist. A police officer may legally search premises and persons where the officer's safety is at risk, the suspect might flee, other criminal acts may be committed, or in other urgent scenarios.
You can always consent to a search or decide to continue talking with the police in an effort to cooperate. In that case, you have waived your right to privacy and the protections of the Fourth Amendment. (This is not to say that you have waived any right to a Miranda warning, as discussed below). When you consent to a search, any evidence that comes to light because of your consent is considered by the courts to have been legally obtained. However, your consent must be given freely and voluntarily. The U.S. Supreme Court has said that "consent that is the product of official intimidation or harassment is not consent at all."