This chapter focuses on the degree of force an officer may use. The Fourth Amendment protects against unreasonable searches and seizures.It requires a warrant, based on probable cause, for searches. It enables law enforcement officers to handle emergency situations that present a compelling need for official action, without time to secure a warrant. Under the Fourth Amendment, an officer may use only such force to detain a person as is "objectively reasonable" under the circumstances. This case is about whether police officers can be held accountable when they lie," lawyers brace for 4th Amendment SCOTUS case. The Fourth Amendment to the United States Constitution protects people from unreasonable searches and seizures. The Fourth Amendment generally requires police to obtain a warrant before conducting a search. The 4 th Amendment to the US Constitution protects you from unreasonable searches and seizures. As a general rule, the Fourth Amendment requires police to have a warrant to conduct a search.