In legal citations, supra and infra are Latin shortcuts that point readers to other parts of the same document: supra (“above”) sends the reader back to a source already cited in full, while infra (“below”) sends the reader forward to material that appears later. They look similar, but they follow different Bluebook rules, and mixing them up is a quick way to confuse a reader working through your footnotes.
How Supra Works
Supra is a short-form citation. Once you have given a source its full citation somewhere earlier in the document, you can refer back to it by writing the author’s last name, a comma, supra, the word “note,” and the footnote number where the full citation lives. A pinpoint page follows after “at.”1Legal Information Institute. Supra
A typical example: Ackerman, supra note 5, at 1425. That tells the reader the full citation sits in footnote 5 and the specific page is 1425.
The rule is strict about direction. The full citation must already exist above the footnote using supra. You cannot point supra at a source that appears for the first time later in the document.
How Infra Works
Infra does the opposite job. It tells the reader that the relevant material is coming up later in the piece.2Legal Information Institute. Infra Writers reach for it when they want to flag a point in an introduction or early section and tell the reader where the full discussion is going to appear.
Under Bluebook Rule 3.5, infra can point to text, individual footnotes, groups of footnotes, or collections of authorities later in the document.3The Bluebook Online. Bluebook Rule 3.5 Internal Cross-References Valid targets include section headings, part numbers, figures, and page ranges. Common formats include see infra note 121, see infra Part II, see infra Figure 5, and see infra notes 35-38 and accompanying text. The wording is flexible; the direction is always forward.
Both terms are always italicized. They are Latin terms of art, and italics mark them off from the surrounding English in the footnote.
Which Sources Can Use Supra
This is where supra and infra part ways with each other, and where most formatting mistakes happen. Under Bluebook Rule 4.2(a), supra is only allowed for certain categories of sources:
- Books
- Journal articles
- Reports
- Pamphlets
- Unpublished materials
- Nonprint resources
These are the secondary materials whose full citations tend to be long and cumbersome, so a shorthand reference saves real space.
Supra is prohibited for most primary authorities. You cannot use it for cases, statutes, constitutions, legislative materials (hearings are the exception), restatements, model codes, or regulations. Each of those has its own short-form rule. Cases use a truncated case name. Statutes repeat enough of the citation to identify the provision. Constitutions are short enough to cite in full every time. Reaching for supra to cite a case or a statute in a brief is a formatting error that signals carelessness.
Supra Versus Id.
Both supra and id. look backward, but they are not interchangeable. The Bluebook sets a clear order: use id. first, and only fall back on supra when id. will not work.
Under Rule 4.1, id. is required when you are citing the same source as the immediately preceding footnote and that preceding footnote contains only one authority. It is the tightest possible cross-reference, essentially saying “same source as the footnote right above.” You can add a different pinpoint page after id. if you are pointing to a different part of the same work.
Id. breaks down in two situations:
- The preceding footnote cites more than one source, which makes id. ambiguous because the reader cannot tell which one you mean.
- Other citations have appeared between the original full citation and the current footnote, so id. no longer points to the right place.
In either situation, you switch to supra (for secondary sources that qualify under Rule 4.2(a)) or to the appropriate short form for the type of primary source you are citing. The practical difference: id. only reaches one footnote back, and only when that footnote is unambiguous, while supra can reach any number of footnotes back as long as the full citation exists somewhere above.
Using Hereinafter With Supra for Long Titles
Some sources carry titles so long that even a supra citation feels bulky. The Bluebook’s answer is hereinafter, which lets you assign a custom short name in the first full citation and then use that short name with supra throughout the rest of the document.
The format has a quirk worth getting right. The word “hereinafter” sits inside square brackets and is not italicized, but the short name that follows it is italicized. A first citation might end with [hereinafter Climate Report]. Later references would then read something like Climate Report, supra note 14, at 38.
Hereinafter earns its keep with government reports, international agreements, and institutional publications whose official titles run a dozen words or more. Pick a short name distinctive enough that the reader will not confuse it with another source in the same document.