You have the right to be secure against unreasonable search and seizure, which limits the police and government power to search you – including your home, body, and personal belongings – but only in situations where you have a reasonable expectation of privacy.
Whether you have a reasonable expectation of privacy in any situation depends on many factors. The law asks whether, in each situation, your desire to be left alone is more or less important than the government’s goals – such as investigating crime – which might involve violating your privacy.
For example, it is reasonable for a person to expect privacy in their things, so police generally cannot look through your bag without a warrant, your permission, or other legal authorization. But if a person is travelling on an airplane (a situation with serious security concerns), a person may not have the same expectation of privacy in their suitcase.
The purpose of this right is to prevent unjustified searches before they happen, not just addressing injustices after they happen.