| --- |
| license: other |
| license_name: mixed |
| pretty_name: Citation-Checker Benchmark |
| language: |
| - en |
| size_categories: |
| - n<1K |
| task_categories: |
| - text-classification |
| tags: |
| - legal |
| - citations |
| - hallucination-detection |
| - benchmark |
| configs: |
| - config_name: charlotin-train |
| data_files: |
| - split: train |
| path: data/charlotin-train/labels.csv |
| - config_name: charlotin-test |
| data_files: |
| - split: test |
| path: data/charlotin-test/labels.csv |
| - config_name: ai-gen |
| data_files: |
| - split: test |
| path: data/ai-gen/labels.csv |
| --- |
| |
| # Citation-Checker Benchmark |
|
|
| A benchmark of whole legal briefs with hand-labelled citations, together with the reports that |
| four citation checkers produced on those briefs: Westlaw, Lexis+, isthiscasereal.com and |
| Hallucite. Every checker was given the same document and its report was aligned to the labels. |
|
|
| The inputs and labels are in `data/`; the checkers' raw output and our parsed results are in |
| `results/`. |
|
|
| ## Components |
|
|
| Each component is a separate config. Components are scored and reported separately, never |
| pooled. |
|
|
| | config | split | documents | labelled citations | what it is | |
| |---|---|---|---|---| |
| | `charlotin-train` | `train` | 40 | 567 | Filings from cases in Damien Charlotin's AI Hallucination Cases database, mostly cases dated March-July 2025, plus a few early well-known cases and every S.D. Tex., W.D. Okla. and E.D.N.Y. case in the database at the time. Compiled in July 2025. | |
| | `charlotin-test` | `test` | 9 | 158 | A random sample of cases in the same database, taken in October 2026. | |
| | `ai-gen` | `test` | 16 | 214 | Motions to dismiss drafted by LLMs from real federal complaints. | |
|
|
| Together that is 65 documents and 939 citations. |
|
|
| **`charlotin-train` was used to improve Hallucite**, so it is not a fair benchmark for comparing |
| Hallucite with the other checkers. The split names reflect this. `charlotin-test` and `ai-gen` |
| played no role in developing Hallucite. |
|
|
| ### The Charlotin components |
|
|
| Charlotin's database typically links only to a court order, not to the filing that contained the |
| hallucinated citations. For each case we tried to find the original filing. When we could not |
| obtain it (filings were sometimes stricken from the record), we either skipped the case or used |
| the court order instead, so some documents here are orders rather than filings. The database |
| stores metadata about the cases, not the documents; the text is public court record, included |
| here as extracted. |
|
|
| ### `ai-gen` |
|
|
| Complaints filed in 2024 or 2025, with embedded text between 10,000 and 32,000 characters, were |
| sampled evenly across S.D. Tex., W.D. Okla. and N.D. Okla. Each of eight models was given a |
| complaint and a minimal prompt and asked for a motion to dismiss: GPT 4o, GPT 5, GPT 6-Sol, |
| Claude 4 Sonnet, Claude 5 Sonnet, Gemini 2.5 Flash, Gemini 3 Flash and Gemini 3.8 Flash. The |
| models were accessed through OpenRouter with default temperature, default reasoning levels and |
| no tools (no internet access). No model was asked to fabricate citations. The briefs are model |
| output, not real filings. |
|
|
| ## Files |
|
|
| ``` |
| data/<config>/<document>.txt the document's text (also .docx: the same text, reflowed) |
| data/<config>/labels.csv one row per citation occurrence (the dataset viewer shows this) |
| data/<config>/documents.csv per-document metadata (briefs.csv for ai-gen) |
| results/<system>/<config>/ each system's raw output, exactly as produced |
| results/<system>/ledger.<config>.csv our parsed result: one row per labelled citation |
| ``` |
|
|
| A document's id is its filename stem. Raw results and the label file's `case_file` column use |
| the same stem, so everything joins back to its input. |
|
|
| The `.docx` files were uploaded to Westlaw and Lexis; they carry the same text as the `.txt` |
| with lines reflowed into paragraphs and page-number lines dropped, because Lexis cannot read a |
| citation that crosses a line break. isthiscasereal.com was given the same reflowed text (pasted, |
| in pieces of at most 15 citations, since it accepts at most 20 per request). |
|
|
| ## Labels |
|
|
| For each document we extracted all full case citations (short-form citations and citations |
| without a case name are excluded) and labelled each by hand, based on a search of Westlaw or |
| Lexis. `labels.csv` has one row per citation occurrence. |
|
|
| | column | meaning | |
| |---|---| |
| | `case_file` | the document's filename stem | |
| | `cite_idx` | 0-based position of the citation in the document, in order of appearance | |
| | `citation_text` | the citation as written | |
| | `citation` | the cite alone, `volume reporter page`, normalized (e.g. `556 U.S. 662`) | |
| | `validity` | `strict`, `referential` or `invalid` | |
| | `parallel_citation` | a second cite to the same case, where the brief gave one | |
| | `correct_case_name`, `correct_citation` | for `referential` rows, the correction | |
| | `src_same_case_name`, `src_same_citation` | for an `invalid` citation that resolves to a real case with a different name, that case's name and citation | |
| | `src_notes` | provenance notes carried over from the source | |
|
|
| `validity`: |
|
|
| - **`strict`**: the citation is valid, allowing for reasonable variations in the case name. |
| - **`referential`**: a reader can recover the intended authority despite an understandable typo |
| in one party name or one component of the reporter citation, with no other errors. |
| - **`invalid`**: the authority does not exist, or the reader cannot recover it from what is |
| written. An invalid citation whose reporter cite points to a real case with an entirely |
| different name is a *collision* (`src_same_citation` is filled in); otherwise it is |
| *nonexistent*. |
|
|
| Citations are judged as the author wrote them: OCR or extraction noise in the text is not the |
| author's error. Systems are scored under two standards: flagging only `invalid`, and flagging |
| `invalid` plus `referential`. |
|
|
| Non-case authorities such as statutes and rules are not labelled. |
|
|
| ## Systems and results |
|
|
| | system | product | input | run dates (2026) | |
| |---|---|---|---| |
| | `westlaw` | Westlaw Advantage, Litigation Document Analyzer ("Check your work") | the `.docx` | Oct 1-9 (`charlotin-train`), Oct 3-4 (`charlotin-test`), Oct 6-7 (`ai-gen`) | |
| | `lexis` | Lexis+ Brief Analysis | the `.docx` | same dates as Westlaw | |
| | `isthiscasereal` | isthiscasereal.com | the reflowed text, in pieces | Oct 8-14 (`charlotin-train`), Oct 8 (others) | |
| | `hallucite` | Hallucite | the `.txt` | Oct 14 (`charlotin-train`), Oct 4 (`charlotin-test`), Oct 7 (`ai-gen`) | |
|
|
| These products change without notice, so the dates matter. Raw output is stored as the |
| system produced it: Westlaw's full report as `.rtf` (Word download), Lexis's report page as |
| `.mhtml` (Chrome "Single File"), isthiscasereal.com's report pages as `.html`. Hallucite has no |
| raw folder here, only a ledger. |
|
|
| ### Ledgers |
|
|
| `results/<system>/ledger.<config>.csv` is our parse of the raw output, joined to the labels. It |
| can be regenerated from the raw files and the labels. One row per labelled citation. |
|
|
| | column | meaning | |
| |---|---| |
| | `system`, `component`, `case_file`, `cite_idx`, `citation`, `citation_text` | which citation | |
| | `finding` | `citation_issue` (the system explicitly warned), `listed` (returned, nothing raised) or `absent` (the output never mentions it) | |
| | `flagged` | 1 if `finding` is `citation_issue` | |
| | `found` | 1 if the system mentioned the citation at all | |
| | `validity` | the label, copied from `labels.csv` | |
| | `vendor_case_name`, `vendor_citation` | what the system printed for this citation | |
| | `joined_on` | how the system's entry was matched to the label: `citation` (exact), `parallel_citation`, `case_at_citation`, or `pincite` | |
| | `vendor_section`, `vendor_resolution`, `vendor_reason`, `treatment_flag` | system-specific fields | |
|
|
| How findings are read: |
|
|
| - A citation is invalid if the system flags it as problematic, and valid otherwise. A citation |
| the system's output never mentions is `absent` and is counted as wrong whatever the label: |
| silence is not the same as checking a citation and finding nothing. |
| - No case-name matching is involved. If a system lists a different case under the citation and |
| says nothing, that is its judgment (`listed`); `vendor_case_name` beside `citation_text` lets |
| you see the substitution. |
| - Treatment flags (KeyCite, Shepard's) are not read as validity signals. |
| - Hallucite's `invalid`, `uncovered` and `unpublished` statuses are warnings; `exists` and |
| `incomplete` are `listed`. `uncovered` means the reporter is outside Hallucite's data, so it |
| could not confirm the citation; scoring that as a flag matches how the other systems treat |
| citations they hold no data for. |
|
|
| ## Limitations |
|
|
| - Labels are hand-made and may contain errors. |
| - `charlotin-train` was used to improve Hallucite (above). |
| - Westlaw, Lexis and isthiscasereal.com were used through their web interfaces and Hallucite |
| was run locally. Vendor products change, so these are results for those dates, not for the |
| products in general. |
| - Some Charlotin documents are court orders rather than the original filings. |
| - `ai-gen` briefs contain fabricated citations produced by language models. They are not |
| real filings. |
|
|
| ## License and provenance |
|
|
| The labels, ledgers and this README are released under CC-BY-4.0. The Charlotin documents are |
| public court records. The `ai-gen` documents are text generated by language models from public |
| complaints. The files under `results/westlaw`, `results/lexis` and `results/isthiscasereal` are |
| the output of those services and remain subject to their owners' terms. |
|
|
| To request removal of anything here, contact bl759@cornell.edu. |
|
|
