How to Use Id. in Bluebook Citations

One of the most common questions undergraduate legal writers encounter is deceptively simple: when can you use Id. instead of repeating an entire citation?

The abbreviation appears throughout legal scholarship, judicial opinions, and law review articles. Understanding it will help you write clearer footnotes and avoid unnecessary repetition.

What Does Id. Mean?

Id. is an abbreviation of the Latin word idem, meaning "the same."

In legal citations, it refers to the immediately preceding authority when that reference is sufficiently clear under the applicable Bluebook rules.

Instead of repeating an entire citation, an author can use Id. to direct the reader to the same source.

Example: Repeating a Case Citation

Consider these two consecutive footnotes:

In this example, the second footnote refers to the same case and page identified in the first footnote.

How to Cite a Different Page

You can also use Id. when citing another page of the same source.

The second footnote refers to page 495 rather than page 494.

When You Cannot Use Id.

You generally cannot use Id. to refer back to one authority when the immediately preceding citation identifies multiple independent authorities.

This second footnote is inappropriate because the preceding footnote contains two separate authorities.

Instead, use an appropriate short-form citation to identify the intended source.

What Happens When Another Citation Intervenes?

Consider this sequence:

Footnote 3 refers to Miranda, not Brown.

If you wish to return to Brown, use a recognizable short-form citation when permitted.

Does Id. Work for Statutes and Articles?

Yes. Id. can be used with many categories of legal authorities, including statutes, cases, and scholarly publications.

The essential question is whether the immediately preceding reference identifies a single authority to which Id. clearly refers.

There are source-specific exceptions and special rules, so consult Bluebook Rule 4.1 for comprehensive requirements.

Formatting Id. Correctly

In Bluebook citations, both the word Id. and its period are italicized.

Use a capital I when Id. begins a citation sentence. Lowercase usage may be appropriate in other contexts.

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Continue Learning

Explore our complete citation guide or read how to cite federal statutes. A tutorial on citing Supreme Court cases is forthcoming.