The United States court system uses the term probable cause to refer to facts or evidence that would make a reasonable person believe that a crime has been committed. Taken from the Fourth Amendment of the Constitution, probable cause, simply put, means the reasonable belief that a person has committed a crime. It is the standard by which an officer or law enforcement agent has the grounds to make an arrest, to conduct a valid search of a person or property, or to obtain an arrest warrant. Probable cause is what is supposed to protect people from unreasonable searches and seizures. Additionally, probable cause is the standard used by a grand jury to determine if they believe a crime has been committed or not.