What was hallucinated

Fabricated: Case Law | Sifuentes cited a 2008 D.C. case titled "In re Search of a Nextel Cellular Telephone" that does not exist; the court found the authority fabricated and not supportive of his proposition. || False Quotes: Case Law | Sifuentes attributes language to Sinclair v. Wainwright that the court found nowhere in that opinion; the panel determined the quoted language does not appear in the cited case. || Misrepresented: Case Law | A reporter citation supplied by Sifuentes retrieves a different case name and does not contain the legal proposition he attributes to it; the court noted the citation did not support his argument.

Sanction teardown · 10th Cir. CA, USA · 2026-02-06

David Angel Sifuentes, III v. Capital One

What happened

In 10th Cir. CA, USA, a filing relied on an unnamed/unconfirmed AI tool to help draft legal argument. The court identified the following problems with the citations in that filing:

Fabricated (Case Law)

Sifuentes cited a 2008 D.C. case titled "In re Search of a Nextel Cellular Telephone" that does not exist; the court found the authority fabricated and not supportive of his proposition.
False Quotes (Case Law)

Sifuentes attributes language to Sinclair v. Wainwright that the court found nowhere in that opinion; the panel determined the quoted language does not appear in the cited case.
Misrepresented (Case Law)

A reporter citation supplied by Sifuentes retrieves a different case name and does not contain the legal proposition he attributes to it; the court noted the citation did not support his argument.

Which AI tool

an unnamed/unconfirmed AI tool. Note: Charlotin's public database records tool attribution only where a court order, brief, or reporting on the matter states it explicitly; "unidentified" or "implied" means the record indicates AI use but does not name a specific product — we do not guess.

Outcome

Not specified in source record.

How Citation Safe would have caught this

Citation Safe runs three deterministic layers before a brief is filed: (1) does the citation exist against CourtListener's database of published opinions, (2) if quoted, does that exact language appear in the source, (3) does the cited case actually support the proposition it is cited for. Fabricated case citations fail Layer 1. Fabricated or misattributed quotations fail Layer 2 even when the underlying case is real. Misrepresented holdings — a real case cited for a proposition it does not support — are the target of Layer 3. None of these checks involve asking another language model whether the citation looks right; they are lookups and text-matches against the actual source, which is why a hallucinated citation has to survive a direct lookup against the authoritative source — not another model's opinion — to earn a VERIFIED stamp; our measured false-verify rate is published live at /quality.

Check a brief before you file it → · See our live false-verify rate

Source: https://www.damiencharlotin.com/documents/1502/DAVID_ANGEL_SIFUENTES_III_Plaintiff_-_Appellant_v_CAPITAL_ONE_Defendant_-_.pdf, via Damien Charlotin's public AI Hallucination Cases Database (CC0).

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