Guide
Look the citation up by volume, reporter and page in a free case-law database, make sure the case at that page is the one named, then open the opinion and find the quoted words and the passage the sentence relies on. Free tools are enough for one citation. A filed brief carries about 53, which is where a checker helps.
In "Ashcroft v. Iqbal, 556 U.S. 662, 678 (2009)" the case name is Ashcroft v. Iqbal, the volume 556, the reporter U.S., the first page 662, the pin cite 678 and the year 2009. A Westlaw or Lexis id such as 2023 WL 1234567 has no volume and page, and no free database can look it up.
CourtListener, run by the non-profit Free Law Project, has a free citation lookup at courtlistener.com/c/: enter the citation and it goes to the case, if it holds one there. Google Scholar's case law search is the other free route: search the citation in quotation marks. Note which case the citation lands on.
A real citation can hold a different case. In one brief filed in federal court, Bostock v. Clayton County was cited at 509 U.S. 644; that page is Shaw v. Reno, and Bostock is at 590 U.S. 644. Compare both party names, and allow for abbreviations (Dep't, Cnty., Ass'n) and for consolidated cases filed under another name.
The pin page has to fall inside the opinion, after its first page and before the next case begins. Case-law sites mark the reporter's page breaks in the opinion text (for example *678). Go to that page and read around it.
Search the opinion for four or five distinctive words from the quote, not the whole sentence: courts drop citations, add brackets and change capitals. If the words sit inside quotation marks in the opinion, the case is quoting another case, and the citation should say "(quoting ...)". If the words are nowhere in the opinion, the quotation is not from this case.
Ask three questions. Does it say what your sentence says, or the opposite? Is the court saying it, or reporting a party's argument or a dissent? Is it the holding, or a passing remark? Courts sanction this failure as well: in the sanctions decisions we classified, about a third of the problems were real cases misused, not invented ones.
This takes a citator: KeyCite on Westlaw or Shepard's on Lexis. Free case-law sites can list the later opinions that cite a case, but they do not tell you which ones overruled or limited it.
A miss in a free database is not proof that the case does not exist. Before you conclude that, rule out the ordinary reasons:
If the case is still nowhere and the citation came from a language model, treat it as unconfirmed until you have the opinion in hand.
proofread.law does steps 2, 3 and 5 for every citation in a draft at once. It looks each one up in a register of 10.1 million US cases built from CourtListener's bulk data, with federal appellate opinions from govinfo added, compares the name and searches the opinion for the quoted words. Every row shows the register entry it relied on, so you can check it against the source. Step 6 is the opt-in deep check: it shows you the passage it found, and at the confidence it shows it confirms 55.0% of good citations and marks a wrong passage as support for 4.5% of wrong pairs. Treat it as a review queue. Step 7 it does not do; it is not a citator.
For a single citation you want to read in full, CourtListener is the better tool: it is free, and the opinion, the docket and the citing cases are in one place. For a draft with fifty citations, paste it into the checker and read the short list it returns. See a sample report, how often each check is wrong, or what the free checkers cover.
ProofreadChecking the other side's brief
The citation is right if the opinion at that volume and page carries the name you cited. A case with that name somewhere else does not confirm the citation. If the case at that citation has a different name, the citation does not point to the case you meant, even though a case exists there.
That CourtListener does not hold it at that citation, which is not the same as the case not existing. Check whether it is a Westlaw or Lexis id, a recent volume, an unpublished decision or another citation for the same case, then search by party names and year.
Check every one. In our measurement of paragraphs drafted by three language models, 7% to 21% of the citations pointed to no case or to a different case, and 4% to 14% quoted words the opinion does not contain.
No. Whether the case exists, carries that name and contains the quotation is one question. Whether a later court overruled or limited it is another, and it needs a citator such as KeyCite or Shepard's.