Supra and infra are Latin signals used in legal citations to send the reader to a full citation that lives elsewhere in the same document: supra means “above” and points backward, infra means “below” and points forward. Neither signal is a citation on its own. Each works only because a complete citation appears somewhere else, and the signal tells the reader exactly where to find it. Using them correctly is a matter of knowing which sources allow supra, how to format the reference, and how to keep the internal numbering accurate as the document changes.
What Each Signal Does
Think of supra and infra as bookmarks built into the text. “Supra note 15” tells the reader the full citation sits back at footnote 15. “Infra Section III” tells the reader a fuller discussion is coming later. In a brief or law review article that references the same source dozens of times across many pages, these signals keep the document readable while still giving the reader a clear trail.
Both signals are always italicized. That visual cue is how readers spot them instantly as navigation rather than part of a title or sentence.
When Supra Is Allowed
Supra is governed by Bluebook Rule 4.2, and it applies only to certain categories of sources. You can use it for books, law review articles, pamphlets, reports, unpublished materials, nonprint resources, treaties, legislative hearings, court filings, and decisions of intergovernmental organizations.1The Bluebook Online. 4.2 Supra and Hereinafter
Supra should not be used for cases, statutes, constitutions, legislative materials other than hearings, restatements, model codes, or regulations.1The Bluebook Online. 4.2 Supra and Hereinafter Each of those primary sources has its own short-form system, and using supra for any of them is treated as an error. A narrow exception exists when a source name is extraordinarily long and no reasonable short form works, but that situation almost never comes up.
How to Format a Supra Citation
A standard supra citation contains the author’s last name, a comma, supra in italics, the word “note” in regular type, the footnote number where the full citation first appeared, and a pinpoint page if you are citing a specific page:
O’Neill, supra note 15, at 52.
If you’re citing the work as a whole rather than a specific page, drop the pinpoint:
O’Neill, supra note 15.
When a source has no individual author, use the title of the work in place of the author’s name. For an edited anthology or similar collected work, use the title of the collection rather than the individual contributor’s name. The word “note” is not italicized. A comma separates the author (or title) from supra, and another comma separates the note reference from the pinpoint.
The footnote number has to be right. A citation that reads “supra note 12” when the full citation now sits at footnote 14 defeats the entire purpose of the signal and sends the reader to the wrong source with no way to find the correct one.
When to Use Infra
Infra is the forward-looking equivalent, governed by Bluebook Rule 3.5. It points the reader to discussions, footnotes, or sections that appear later in the same document.2The Bluebook Online. 3.5 Internal Cross-References
It earns its keep when you mention a legal principle early and save the detailed analysis for a later section. Rather than front-loading the introduction, you can write “See infra Section II.C” and move on, confident the reader knows where the deeper treatment lives. That keeps the argument in a logical order.
Accuracy matters here as much as with supra. If you reorganize a brief and shuffle sections, every infra reference has to be updated to match the new structure. A cross-reference pointing to a section that no longer exists, or one that now covers a different topic, reads as careless.
Choosing Between Id. and Supra
New legal writers often confuse id. and supra because both refer back to something already cited. The line is straightforward: id. refers to the immediately preceding citation, while supra can reach back to any earlier footnote.
Under Bluebook Rule 4.1, use id. when the source is the same one referenced in the footnote directly above. If you’re citing a different page of that same source, write “Id. at [new page].” The catch is that id. only works when the preceding footnote contains a single source. If the footnote above cites multiple authorities, id. is ambiguous, and you have to switch to supra with the specific footnote number.
The practical rule: use id. whenever you can, because it’s the shortest and cleanest. Fall back to supra when id. does not work, either because another source has intervened or because the preceding footnote contains multiple citations. Id. is always italicized, including its period.
What to Use Instead of Supra for Cases and Statutes
Because supra is off-limits for primary sources, cases and statutes each have their own short-form method.
Cases
Under Bluebook Rule 10.9, once you have provided a full case citation, later references use an abbreviated form containing one party’s name and the volume and reporter information. After citing Stone v. Powell, 428 U.S. 465 (1976) in full, a later reference can read Stone, 428 U.S. at 470. You can drop the party name and write 428 U.S. at 470 when context makes the reference unambiguous. If the case was the sole authority in the immediately preceding footnote, use id. instead.
Statutes
Statutes follow Bluebook Rule 12.10. A short form works only if the full citation appeared in the same footnote or within the five previous footnotes. Past that, provide the full citation again. When referring to a different section of the same statute, use id. followed by the new section number rather than “at.” A construction like “42 U.S.C. ยง 1983, supra note 5″ is wrong because statutes do not use supra.
Hereinafter for Unwieldy Titles
Some source titles are long enough that even a supra citation feels clunky. Rule 4.2 lets you assign a short nickname in the first full citation and then use that nickname in every later supra reference.1The Bluebook Online. 4.2 Supra and Hereinafter
The label goes in brackets at the end of the first full citation. “Hereinafter” itself is not italicized, even though supra is:
National Academy of Sciences, Understanding Climate Change: A Program for Action 22 (1975) [hereinafter Understanding Climate Change].
Every later reference then uses the short name: Understanding Climate Change, supra note 8, at 35. Once you create a hereinafter label, use it consistently. Switching back and forth between the full title and the short name in the same document creates confusion.
Common Mistakes That Cost Credibility
The most frequent supra error is using it for cases or statutes. It trips up law students constantly and shows up occasionally in briefs by attorneys who learned citation rules decades ago. If the source is a case, use the Rule 10.9 short form. If it’s a statute, use Rule 12.10. Reserve supra for the secondary sources and other categories listed in Rule 4.2.
Stale footnote numbers are the second common problem. Every time you add or delete a footnote during editing, every supra reference in the document has to be rechecked. Judges and clerks notice when citations don’t check out, and that skepticism can bleed into how they evaluate the substance of the argument.