Administrative searches are significant intrusions upon the interests protected by the Fourth Amendment, that such searches when authorized and conducted without a warrant procedure lack the traditional safeguards which the Fourth Amendment guarantees to the individual, and that the reasons for upholding these warrantless searches are insufficient to justify so substantial a weakening of the Fourth Amendment's protections. The Frank majority gave recognition to the unique character of these inspection programs by refusing to require search warrants; to reject that disposition does not justify ignoring the question whether some other accommodation between public need and individual rights is essential.
The Fourth Amendment provides that, 'no Warrants shall issue, but upon probable cause.' In cases in which the Fourth Amendment requires that a warrant to search be obtained, 'probable cause' is the standard by which a particular decision to search is tested against the constitutional mandate of reasonableness. To apply this standard, it is obviously necessary first to focus upon the governmental interest which allegedly justifies official intrusion upon the constitutionally protected interests of the private citizen. For example, in a criminal investigation, the police may undertake to recover specific stolen or contraband goods. But that public interest ...