Following the September 11, 2001, terrorist attack on the United States, the Department of Justice carried out a general review of existing guidelines and procedures relating to national security and criminal matters. The reissuance of these Guidelines reflects the result of that review.
These Guidelines follow previous guidelines in their classification of levels of investigative activity, in their classification of types of investigations, in their standards for initiating investigative activity, and in their identification of permitted investigative techniques. There are, however, a number of changes designed to enhance the general effectiveness of criminal investigation, to bring the Guidelines into conformity with recent changes in the law, and to facilitate the FBI's central mission of preventing the commission of terrorist acts against the United States and its people.
In their general structure, these Guidelines provide graduated levels of investigative activity, allowing the FBI the necessary flexibility to act well in advance of the commission of planned terrorist acts or other federal crimes. The three levels of investigative activity are: (1) the prompt and extremely limited checking of initial leads, (2) preliminary inquiries, and (3) full investigations. Subject to these Guidelines and other guidelines and policies noted in Part IV below, any lawful investigative technique may be used in full investigations, and with some exceptions, in preliminary inquiries.