How to check a brief for fake or AI-invented citations before you file
By LegiMatch Research Team · Published October 17, 2026 · Updated October 21, 2026 · 6 min read
Short answer: check every citation in the brief against the court's actual opinion - not against memory, a summary, or an AI chatbot. For each case confirm five things: the case exists at that citation, the name matches, the pin cite falls inside the opinion's pages, any quotation appears in the opinion, and the case is still good law. You can do this by hand in a few hours, or upload the brief to a citation-checking tool such as LegiMatch Brief Check and get a flagged report, with links to the real opinions, in about a minute.
Why this matters now
Since 2023, US courts have sanctioned attorneys for filing briefs that cite decisions which don't exist. In Mata v. Avianca, Inc. (S.D.N.Y. 2023) the court imposed a $5,000 sanction after a brief cited cases generated by ChatGPT; in Park v. Kim, 91 F.4th 610 (2d Cir. 2024), an attorney was referred to the court's grievance panel for the same failure. Courts have been consistent: using AI isn't misconduct, but signing a brief certifies that you read the authorities in it. See AI-invented case citations: the sanctions every lawyer should know.
Invented cases are only part of the risk. The same review catches the ordinary errors that cost credibility with a judge: a transposed volume number, a pin cite to the wrong page, a quotation that was paraphrased, or a case that was reversed last year.
The five checks for every citation
| # | Check | What goes wrong | How it looks in a brief |
|---|---|---|---|
| 1 | The case exists at that citation | Invented cases; wrong volume or page | Harrington v. Calloway Freight Lines, 912 F.3d 4471 - no such page |
| 2 | The case name matches the citation | A real citation attached to the wrong name - the most common sign of an AI-invented cite | "Reed v. City of Albany, 78 N.Y.2d 1" when 78 N.Y.2d 1 is Reed v. State |
| 3 | The pin cite is inside the opinion | A pinpoint page outside the opinion's page range | "925 F.3d 541, 560" when the opinion runs 541-552 |
| 4 | Quotations are word-for-word | Paraphrase in quotation marks; language that isn't in the opinion at all | A quoted holding no court wrote |
| 5 | The case is still good law | Reversed, overruled, or questioned by a later decision | Relying on a decision a higher court has since overruled |
How to do it by hand
- List every authority. Go through the brief and write down each case, statute and rule, with the pages of the brief where it appears. (This also gives you the start of your table of authorities.)
- Pull each opinion from a reliable source - an official reporter, the court's website, or a legal research database. Never rely on a summary or a chatbot's description.
- Compare the citation line: name, volume, reporter, first page, court and year.
- Open the pin cite page and confirm the proposition is actually there.
- Search the opinion for each quotation, word for word.
- Check later history: has the case been reversed, overruled, or criticised? Use a citator if you have one; otherwise see how to check good law without Westlaw.
- Read the cases you rely on most. No tool replaces reading the authority.
For a 25-page brief with 30-40 authorities, a careful manual cite check typically takes a paralegal or associate several hours.
How to do it automatically with LegiMatch Brief Check
- Upload the brief as PDF or Word, or paste the text.
- LegiMatch compares every case citation with the stored court opinion and returns a report in about a minute:
- Error - the pin cite is outside the opinion, the case name doesn't match the citation, a quotation isn't in the opinion, or the case was treated negatively by a later decision
- Warning - the case isn't in the library (verify it in an official reporter; it may be real), one party's name differs, or the year or court doesn't match
- OK - the citation matches the opinion
- Statute citations are checked too: a section that doesn't exist, a repealed section, a table-of-authorities entry the brief never cites, and - with AI - a real section cited for a point it isn't about.
- Every flagged case links to the real opinion so you can confirm in one click; a likely correct citation is suggested ("did you mean"), and a misquotation is shown side by side with the opinion's words.
- Download the report and a ready-made table of authorities as PDF or Word, or run the same check inside Microsoft Word with the add-in.
In our published blind tests on real court documents, Brief Check caught 98.6% of planted citation mistakes and called none of 5,185 real citations fake.
Brief Check is unlimited on every LegiMatch plan and in the 14-day free trial. To check a few citations without an account, use the free citation checker.
What a citation check can't do
- It can't tell you the case supports your argument. It confirms the citation is accurate, not that the reasoning helps you. Read the authorities.
- "Not found" isn't the same as "fake". Every database has gaps - unpublished decisions, very recent opinions, some older cases. Verify anything not found before you conclude it doesn't exist.
- It doesn't replace your judgment on whether a negatively treated case is still usable for your point.
Frequently asked questions
How do I check if a case citation is real?
Find the opinion at the cited volume and page in an official reporter, the court's website, or a legal research database, and confirm the case name, court and year match. A brief-checking tool such as LegiMatch Brief Check does this for every citation in the document at once and links each one to the real opinion.
Can I ask ChatGPT to check my brief's citations?
It isn't a reliable check. General-purpose chatbots answer from patterns in their training data, not by opening the court's opinion, so they can confirm a citation that doesn't exist or describe a real case incorrectly. Check citations against the opinion text itself. See LegiMatch vs ChatGPT for checking citations.
What is the most common sign of an AI-invented citation?
A real-looking citation attached to the wrong case name, or a citation whose page number doesn't exist in that reporter volume. Both are caught by comparing the citation with the stored opinion.
How long does a citation check take?
By hand, several hours for a typical brief with 30-40 authorities. With LegiMatch Brief Check, about a minute, followed by your review of anything flagged.
Is there a free brief citation checker?
LegiMatch has a free citation checker that needs no sign-up and shows whether case citations match real court opinions. Full Brief Check - names, pin cites, quotations, treatment and a table of authorities - is included in the 14-day free trial.
Does checking citations satisfy Rule 11?
Rule 11 requires that the legal contentions in a filing be warranted by existing law, which in practice means you read and confirm the authorities you cite. An automated check is a strong safeguard against errors, but you remain responsible for reading the cases you rely on.
Sources
- Mata v. Avianca, Inc., No. 22-cv-1461 (PKC) (S.D.N.Y. June 22, 2023) (opinion and order on sanctions)
- Park v. Kim, 91 F.4th 610 (2d Cir. 2024)
- ABA Standing Committee on Ethics and Professional Responsibility, Formal Opinion 512, "Generative Artificial Intelligence Tools" (July 29, 2024)
- Fed. R. Civ. P. 11(b)
This article is general information about legal research, not legal advice. Verify every authority before relying on it.
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