Top Law Firm Sullivan & Cromwell Admits AI Hallucinations in Court Filing

In a rare public admission, Sullivan & Cromwell (S&C), one of the world’s most prestigious and profitable law firms, has acknowledged submitting court filings containing AI-generated "hallucinations"—fabricated case citations and misquoted authorities.

The revelation comes after Boies Schiller Flexner (BSF), a rival litigation firm, flagged the errors in a filing submitted by S&C on April 9, 2026. The filing, an Emergency Motion for Entry of Orders Granting Ex Parte Relief, included inaccuracies later detailed in a correction letter by S&C senior partner Andy Dietderich.

How the AI Errors Were Discovered

Boies Schiller Flexner, a firm previously criticized for its own AI-related mistakes, identified the errors in S&C’s filing. This adds a layer of irony, as BSF had been the subject of a high-profile AI blunder in 2024, where it failed to catch AI-generated errors in a co-counsel’s filing.

S&C’s Public Apology and Internal Failures

In a letter addressed to the court, Dietderich—joining S&C nearly 30 years ago and a Chambers Band 1 bankruptcy lawyer—acknowledged the mistakes without deflecting blame. His letter stated:

"I became aware Thursday evening that the JPLs' Emergency Motion for Entry of Orders Granting (I) Ex Parte Relief and (II) Provisional Relief, Pursuant to Section 1519 of the Bankruptcy Code filed with the Court on April 9, 2026 (the 'Motion') includes inaccurate citations and other errors, each of which is identified and corrected in Schedule A to this letter. The inaccuracies and errors in the Motion include artificial intelligence ('AI') 'hallucinations.'"

Dietderich’s letter further revealed that S&C’s internal policies and training on AI use were not followed in preparing the motion. The firm’s review process also failed to catch the errors, which appeared to stem from both AI-generated content and manual mistakes.

Why This Matters for the Legal Industry

This incident underscores the risks of AI adoption in high-stakes legal work. Sullivan & Cromwell, which prominently features its advisory role on OpenAI’s "safe and ethical deployment" of AI on its website, now joins a growing list of elite firms—including Boies Schiller Flexner—embroiled in AI-related legal missteps.

Unlike many firms that may hide such errors, S&C’s transparency in acknowledging the mistakes and Dietderich’s willingness to take responsibility reflect a rare level of accountability in the legal profession.