- This article is part of a series on Litigation
A Vaughn Index is a document prepared by agencies that are opposing the disclosure of information under FOIA. The index must describe each document (or portion of each document) that has been withheld and provide a detailed justification of the agency’s grounds for non-disclosure (i.e., the FOIA exemption relied upon must be stated). The term originates from the case of Vaughn v. Rosen 
Vaughn Indices are intended to permit a court “to make a rational decision [about] whether the withheld material must be produced without actually viewing the documents themselves.”  They are intended also to help "create balance between the parties." 
Note that a Vaughn Index can sometimes be useful in a non-litigation setting, but the Vaughn ruling does not require that agencies prepare an itemized index of withheld documents in the context of the administrative process. A requester whose FOIA request is pending in the administrative stage of processing is not entitled to a Vaughn index. 
A Vaughn Index must: (1) identify each document withheld; (2) state the statutory exemption claimed; and (3) explain how disclosure would damage the interests protected by the claimed exemption." 
The description of the withheld material must be “sufficiently specific to permit a reasoned judgment as to whether the material is actually exempt under FOIA.”
If a court finds that an index is not sufficiently detailed, it will often require the relevant agency to provide one that is more detailed. 
Alternatively, if a Vaughn Index is inadequate to support withholding, courts have sometimes utilized in camera review of the withheld material. See In Camera Inspection
The Vaughn Index can take many forms such as a straight affidavit, a narrative document, an affidavit with a chart or index detailing the withholdings attached, or a hybrid of any of these examples. The types and size of the withholdings will often dictate the format the declaration takes. (For instance, if only a few pieces of information are withheld, a simple affidavit justifying them will most likely be more than adequate. However, a case involving hundreds, or even thousands of documents, and probably thousands of redactions will require more than a small affidavit.) 
Some agencies use coded Vaughn Indices which break certain FOIA exemptions into several categories, explain the particular nondisclosure rationales for each category, and then mark the exemption and category on the particular documents at issue.
Recent district court cases regarding Vaughn Indices
- 484 F.2d 820 (D.C. Cir. 1973), cert. denied, 415 U.S. 977 (1974)
- King v. Dept. of Justice, 830 F.2d 210, 219 (D.C. Cir. 1987).
- Long v. DOJ, 10 F. Supp. 205, 209 (N.D.N.Y. 1998)
- https://ogis.archives.gov/Resources/the-ogis-library/vaughn-index_s1_p214.htm. See also Bangoura v. U.S. Dep't of the Army, 607 F. Supp. 2d 134, 143 n.8 (D.D.C. 2009)
- Citizens Comm'n on Human Rights v. FDA, 45 F.3d 1325, 1326 n.1 (9th Cir. 1995).
- Founding Church of Scientology v. Bell, 603 F. 2d 945, 949 (D. C. Cir. 1979).
- See, for example, Citizens for Responsibility & Ethics in Wash. v. DHS <648 F. Supp. 2d 152, 157-58 (D.D.C. 20090; Defenders of Wildlife v. U.S. Border Patrol 623 F. Supp. 2d 83, 88-89 (D.D.C. 2009); Schoenman v. FBI 604 F. Supp. 2d 174, 202 (D.D.C. 2009); McGehee v. DOJ. 800 F. Supp. 2d 220, 238 (D.D.C. 2011)
- Jones v. FBI, 41 F.3d 238, 242 (6th Cir. 1994); Gallant v. NLRB, 26 F.3d 168, 172-73 (D.C. Cir. 1994)
- Judicial Watch, Inc. v. USPS, 297 F. Supp. 2d 252, 257 (D.D.C. 2004)
- Landmark Legal Found. v. IRS, 267 F.3d 1132, 1138 (D.C. Cir. 2001)
- Hodge v. FBI, 764 F. Supp. 2d 134, 141 (D.D.C. 2011); Blackwell v. FBI, 680 F. Supp. 2d 79, 95 (D.D.C. 2010)