# AI Legal Citation Checker — Verify Cases Before You File

> Check whether the cases in an AI-drafted brief actually exist. RankShield Legal resolves each citation against live case-law and issues a verifiable certificate before you sign.

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# Check every AI-drafted citation before it reaches the court.
**Paste a citation and RankShield Legal resolves it against live case-law** — confirming the case exists before you rely on it. For a full filing, every authority is certified on three dimensions and sealed into a record you, a court, or your insurer can verify independently.
[Try the citation checker](https://rankshieldlegal.com/ai-legal-citation-checker/) [Request early access](https://rankshieldlegal.com/contact/)

Small and midsize firms are the ones getting caught. Public sanctions trackers now catalog well over a thousand filings that cited cases which do not exist, and the pattern is consistent: a lawyer trusts an AI-drafted brief, the citations look perfectly formatted, and a fabricated authority slips through to a judge. A free citation checker that resolves each case against real case-law closes the most dangerous gap in seconds — and RankShield Legal turns that check into a certificate you can prove you ran. This page explains what the instant check confirms, what full certification adds, and — just as important — what neither of them claims to do.

## How does the citation checker work?
**Existence first.** The checker matches each citation against live case-law by its exact reporter citation, not just the case name. A citation that resolves to no real opinion is flagged as fabricated. Correct Bluebook formatting is never treated as evidence a case exists — AI-fabricated citations copy perfect format. The instant check answers the single most important question about an AI-assisted brief: **is this a real case?** It is the primary anti-hallucination signal, because fabricated cases do not resolve against a live corpus. The tool below runs that existence check against a public case-law source and returns a plain verdict — resolved, or not found. There is no dashboard to learn and no account to create to try it. You paste a citation, and the resolver tells you whether an opinion with that reporter citation actually exists in the corpus it can reach.
For a filing you are about to sign, the full certification goes further: it also matches quoted passages against the published opinion, overlays good-law standing from your firm's citator, and seals the result to a tamper-evident log. The instant checker is the front door; certification is the checkpoint between your draft and your signature. One is a fast sanity check you can run on a single string of text; the other is a durable record of what you verified, when, and against what. You can read the deeper mechanics on [how it works](https://rankshieldlegal.com/how-it-works/).
Both start from the same discipline. The resolver never reasons about whether a case sounds plausible. It looks the citation up. A model can generate a citation that reads exactly like a Ninth Circuit opinion — correct reporter, believable volume and page, a party name that fits the doctrine — and be entirely invented. The only reliable way to separate the real from the fabricated is to check the string against a source of truth, which is precisely what the resolver does and what a human skim, however experienced, cannot do at speed.

Live tool · RS-210
## Check a citation against live case-law
Paste a reporter citation from an AI-drafted brief. We resolve it against a live case-law corpus and tell you whether the case is real. Existence check only — not good-law standing, and not legal advice.

Reporter citation Check
Try a real one like 576 U.S. 644 or a fake one like 999 U.S. 9999.

Resolves against the public CourtListener corpus. Full certification (existence + quotation + good-law, signed and sealed to a transparency log) is part of the RankShield Legal platform. [How certification works →](https://rankshieldlegal.com/citation-certification/)

## What does the free existence check actually confirm?
The free check confirms one thing precisely, and it is careful not to overstate it: an opinion matching the reporter citation you entered exists in the public case-law corpus the resolver reaches. The existence check runs against CourtListener and public case-law sources. That scope is a feature and a boundary at the same time. When a citation resolves, you have strong evidence the case is real. When it does not resolve, you have a clear signal to stop and investigate before that authority goes anywhere near a filing.
It is worth being exact about the limit, because honesty here is the entire value of the tool. The resolver is only as complete as the case-law corpus it reaches. A very recent opinion, a sealed matter, an unpublished disposition, or a citation to a source outside the public corpus may not resolve even though the case is genuine. A non-resolution is a prompt to verify, not a verdict of forgery. What the free check reliably catches is the failure mode that is sinking firms today: a confidently formatted citation to a case that was never decided by any court, because a language model produced it to fill a gap in an argument.
That is the difference between the free existence check and the good-law question people often conflate with it. Existence tells you the case is real. It does not tell you the case is still binding, has not been overruled, or supports the proposition you cited it for. Those are separate dimensions, and full certification handles them separately — because collapsing them into a single green checkmark is exactly the kind of overclaim that gets a tool trusted for something it never measured.

## What does the three-dimension certification cover?
These three dimensions fail independently, which is why certifying only one of them leaves real exposure. A case can exist and be good law but be quoted for a holding it does not contain. A case can exist and be quoted accurately but have been overruled two years ago. A case can be quoted perfectly from an opinion that was never written. Certifying existence alone — the thing most free checkers stop at — closes the loudest failure but leaves the quieter, arguably more damaging ones open. Full [citation certification](https://rankshieldlegal.com/citation-certification/) addresses all three and records the result of each, so the certificate reflects what was actually checked rather than a single blended score.

- **Existence** — the citation is matched exactly against live case-law, so a fabricated case is flagged before you sign. This is the same resolution the free tool performs, now recorded as part of a signed result.
- **Quotation accuracy** — quoted passages are matched against the text of the published opinion, catching misquotes, paraphrases dressed up as direct quotes, and quotations that appear nowhere in the cited case.
- **Good-law standing** — overruled, superseded, or questioned authority is flagged, sourced from your firm's citator (KeyCite or Shepard's). We never guess good law; the standing signal comes from the citator you already trust, and we record what it returned.

## Why does AI fabricate citations that look perfect?
A large language model does not retrieve cases. It predicts text. When it writes a citation, it is generating the most statistically likely sequence of characters that looks like a citation in that context — the right reporter for the circuit, a plausible volume, a party name that fits the doctrine, a pin cite in the expected range. Correct format is the easy part for a model to reproduce, because format is the most regular, most learnable pattern in the entire training corpus. That is the trap. The very thing a hurried reviewer uses as a proxy for legitimacy — clean Bluebook form — is the thing an AI reproduces most faithfully whether or not the underlying case is real.
This is why formatting is worthless as an existence signal and why the checker never treats it as one. Two citations can be byte-for-byte indistinguishable in form; one resolves to a real opinion and one resolves to nothing. Only a lookup separates them. It also explains why the problem hits busy small and midsize firms hardest. The fabricated citation is engineered, by the nature of the model, to survive exactly the review a solo or small team has time for: a glance at the format, a nod at the plausible name, and into the brief it goes. The deeper mechanics of how these fabrications enter filings, and what they cost, are covered on [AI hallucination in legal filings](https://rankshieldlegal.com/ai-hallucination-legal-filings/).

## How large is the fabricated-citation problem?
The numbers are not fringe. A Stanford RegLab study, published in the Journal of Empirical Legal Studies in 2025, found that leading purpose-built legal AI research tools still hallucinate on a meaningful share of queries — roughly 17 percent for Lexis+ and around 33 percent for Westlaw AI — with general-purpose chatbots performing far worse. These are the tools marketed specifically to lawyers, with retrieval built in. The takeaway is not that the tools are useless; it is that a nonzero, meaningful hallucination rate is the baseline you are working with, and that unverified output cannot be trusted at the point of filing.
Public trackers such as the widely cited AI Hallucination Cases database maintained by Damien Charlotin now catalog well over a thousand filings worldwide involving AI-fabricated or misused citations, and the count keeps climbing. The landmark matter, Mata v. Avianca, drew a 5,000-dollar sanction for citations to cases that did not exist; some later matters have reached six figures. The reputational cost — a published opinion naming you, an adversary who now reads every one of your citations with suspicion — is harder to price and often larger than the sanction itself.
17–33% hallucination rate a Stanford RegLab study found across leading legal AI research tools (Lexis+ to Westlaw AI); raw general LLMs far higher
1,000+ filings worldwide cataloged by public trackers as containing AI-fabricated or misused citations (directional, not exact)
$5,000 sanction in Mata v. Avianca, the landmark fabricated-citation matter; some later matters reached six figures

## Why does a signed certificate beat a dashboard flag?
Most citation tools flag a suspected problem and produce nothing durable. A red badge appears in a dashboard, you resolve it, and the badge disappears. When a judge's standing order later asks what you did to verify your authorities, "our tool flagged nothing" is an assertion — a claim about a screen no one else saw, in software the court cannot inspect, at a moment that has already passed. It asks the reader to trust you, and increasingly, courts are not inclined to take that on faith.
A certificate is evidence instead of an assertion. Each result is signed with post-quantum cryptography and sealed to an RFC 6962 transparency log, so a court, opposing counsel, or your insurer can confirm the check ran — what was checked, and that the record has not been altered since — without trusting you or us. The distinction is the whole point: a flag is a transient state inside a vendor's UI, while a certificate is a portable, independently verifiable artifact that outlives the session and travels with the matter. You can see how anyone verifies one on the [transparency](https://rankshieldlegal.com/transparency/) page.

## Flag versus certificate — what is the real difference?
The table is not a knock on flags as a working aid — a flag is a fine way to catch a problem in the moment. It is a statement about what evidence survives the moment. When the question is no longer "did the tool notice" but "can you prove to a third party what you verified," only the right-hand column answers it.
Dimension Typical dashboard flag RankShield certificate
Who can verify it Only you, in the vendor's UI Court, opposing counsel, insurer — independently
Survives the session No — clears when resolved Yes — sealed to a transparency log
Tamper-evidence None; a screenshot proves nothing RFC 6962 inclusion proof; alteration is detectable
What it records A transient warning state What was checked, when, against what corpus
Trust model Trust the vendor and the lawyer Verify the cryptography, trust no one

## Where does the checker fit in your workflow?
Nothing here asks you to abandon the tools you already use or to route privileged work through a black box. The checker sits between drafting and signature as a verification step, not a research replacement. Because it operates on citations rather than on your work product, it fits a small firm's workflow without a litigation-support team to run it. How the underlying material is kept separated from the verification path is described on [privilege isolation](https://rankshieldlegal.com/privilege-isolation/).

- **Draft with any tool** Use whatever research or drafting assistant you prefer. The checker is model-agnostic; it does not care how the citation was produced, only whether it resolves.
- **Run the free existence check** Paste a citation, or a set of them, into the tool below. Each is resolved against public case-law by its exact reporter citation. Non-resolutions are your stop-and-verify list.
- **Certify before you sign** For a filing, run full certification: existence, quotation accuracy against the published opinion, and good-law standing pulled from your citator. Each dimension is recorded separately.
- **Seal and keep the record** The result is signed and sealed to a transparency log. If a standing order or an insurer later asks, you produce a certificate — not a recollection.

## How is the record sealed and independently verified?
Every certificate is signed with composite post-quantum signatures — ML-DSA and SLH-DSA, the algorithms standardized as NIST FIPS 204 and 205 — and sealed to an RFC 6962 transparency log. Composite signing means the record carries two independent post-quantum signatures, so it stays verifiable even if weaknesses are later found in one scheme. The transparency log gives each certificate an inclusion proof: anyone can confirm the record was entered at a specific point and has not been altered since, without contacting us and without trusting us.
One deliberate design choice matters for any lawyer weighing this: the records store digests, never filing substance. A digest is a cryptographic fingerprint of what was checked, not the brief, the quotation, or the client's matter. That is what lets a court or insurer verify that a check occurred and what its result was, while the underlying work product stays with you. Verifiability and confidentiality are not in tension here, because the thing that gets published is a fingerprint, not the document. More on the cryptographic posture is on the [security](https://rankshieldlegal.com/security/) page.

## What is enterprise-grade protection, firm-sized?
Large firms manage citation risk with dedicated litigation-support staff, internal review protocols, and the budget to build accountability into their process. A solo practitioner or a five-lawyer firm carries the same duty of candor to the court and the same malpractice exposure, without any of that infrastructure. The gap is not one of care — small-firm lawyers are not less diligent — it is one of tooling and time. That gap is exactly where the fabricated citation slips through.
The checker is meant to close that gap without adding headcount. The same verifiable accountability a large firm would build in-house is delivered as a checkpoint you switch on: run the existence check for free, certify a filing when it counts, and keep a record you can produce on demand. Enterprise-grade protection, firm-sized, means the control is proportionate to the practice — no team to staff, no platform to administer, just the verification step at the moment it matters most.

## What does this tool not do, and not claim?

- Myth It guarantees an AI that never hallucinates. Truth It never claims to be hallucination-free. It certifies which of your citations are real, accurately quoted, and good law. The model is not the thing we vouch for; the verified citations are.
- Myth The existence check confirms a case is good law. Truth Existence and good-law are different dimensions. The instant checker confirms a case exists; good-law standing comes from your citator (KeyCite or Shepard's) during full certification. We never guess good law.
- Myth It resolves every real case, so a non-resolution means forgery. Truth The resolver is only as complete as the case-law corpus it reaches. A very recent, sealed, or non-public opinion may not resolve although it is genuine. A non-resolution is a prompt to verify, not a verdict.
- Myth It reads your brief and stores your filing. Truth The certified record stores digests — cryptographic fingerprints — never filing substance. Verification confirms what was checked without exposing the underlying work product.
- Myth It is legal advice. Truth RankShield is a security vendor. The output is verifiable technical evidence, not a legal opinion, and it does not replace your professional judgment or your independent duty to verify authorities.

Early access · Law firms
### Prove it, don't promise it
Certify every citation, attest privilege isolation, and seal each result to a log a court or client can verify. Enterprise-grade protection, firm-sized.
[Request early access →](https://rankshieldlegal.com/contact/) [hello@seoeliteagency.com](mailto:hello@seoeliteagency.com)

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## AI Citation Checker, answered
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- **Is the citation checker free?** The instant existence check is free to try: paste a citation and it resolves against a public case-law source, returning whether the case is real. There is no account to create to run it. Full three-dimension certification — existence, quotation accuracy, and good-law standing, signed and sealed to a transparency log — is part of the RankShield Legal platform we are onboarding firms to now. The free check is deliberately useful on its own, because catching a fabricated case before it reaches a judge is the single most valuable thing this tool does.
- **How does it catch a fabricated citation?** Each citation is resolved against live case-law by its exact reporter citation, not just the case name. A citation that does not resolve to a real opinion is flagged. Perfect Bluebook formatting is never treated as proof a case exists, because AI-fabricated citations reproduce correct format — that is exactly why they slip past a human skim. A language model predicts text, so it generates citations that look right whether or not the case is real. The only reliable separator between a genuine and an invented citation is a lookup against a source of truth, which is what the resolver performs.
- **What is the difference between the existence check and good-law standing?** They are separate dimensions and the tool keeps them separate. The existence check confirms that an opinion matching your citation actually exists in the public case-law corpus the resolver reaches. Good-law standing is a different question entirely: is that case still binding, or has it been overruled, superseded, or questioned? We never guess good law. During full certification, good-law standing is pulled from your firm's citator — KeyCite or Shepard's — and recorded. A case can be perfectly real and no longer good law, which is why confirming existence alone is not enough before you rely on an authority.
- **Can a court verify what I checked?** For full certifications, yes. Every certificate is signed with composite post-quantum signatures (ML-DSA and SLH-DSA, NIST FIPS 204 and 205) and sealed to an RFC 6962 tamper-evident transparency log, so anyone can check the inclusion proof independently — without contacting or trusting us. That turns "we checked the citations" from a claim into evidence. The record stores digests, never the substance of your filing, so a court or insurer can confirm a check occurred and what it returned while your work product stays confidential with you.
- **Does a non-resolution always mean the case is fake?** No, and the tool is careful not to imply that. The resolver is only as complete as the case-law corpus it reaches, which runs against CourtListener and public case-law. A very recent opinion, a sealed matter, an unpublished disposition, or a citation to a source outside the public corpus may not resolve even though the case is genuine. Treat a non-resolution as a stop-and-verify signal rather than a verdict of forgery. What the check reliably catches is the dangerous failure mode: a confidently formatted citation to a case no court ever decided.
- **Do I have to change my research or drafting tools to use it?** No. The checker is model-agnostic and sits between drafting and signature as a verification step, not a research replacement. Draft with whatever assistant or database you prefer, then run the citations through the existence check and, for a filing, through full certification. Because it operates on citations rather than on your work product, it fits a small or midsize firm's workflow without a litigation-support team to administer it. You keep your process; you add a checkpoint that produces evidence you verified your authorities.
- **Is this legal advice?** No. RankShield is a security vendor, and this page and the tool provide verifiable technical evidence, not a legal opinion. The certificate confirms which of your citations are real, accurately quoted, and — via your citator — good law; it does not tell you whether a case supports your argument or how to use it. Your professional judgment and your independent duty of candor to the court remain entirely yours. Think of certification as a control that documents your verification, not as a substitute for it.

Keep exploring
## Related work
[Platform Citation Certification Existence, quotation, and good-law standing for every authority — issued as a verifiable certificate, not a flag. Explore →](https://rankshieldlegal.com/citation-certification/)[Solutions AI Hallucinations in Filings Why AI invents citations, what courts now require, and how to catch a fabricated case before signature. Explore →](https://rankshieldlegal.com/ai-hallucination-legal-filings/)[Platform Privilege Isolation A signed attestation that privileged material stayed inside the approved boundary — bound to informed consent. Explore →](https://rankshieldlegal.com/privilege-isolation/)