The search results document several well-known AI hallucination cases in legal filings, primarily:
- Amir Mostafavi (Los Angeles, October 2025): Fined $10,000 for citing 21 fake cases generated by ChatGPT in an appellate brief[3][8]
- LeRoy George Siddell (San Diego): Sanctioned $1,500 for including fabricated citations in a criminal defense case[1]
- Steven A. Schwartz and Peter LoDuca (New York, 2023): Faced sanctions for ChatGPT-generated fake citations in an Avianca airline case[7]
- Rishi Nathwani (Australia, 2025): Apologized for AI-generated fake quotes and citations in a murder case[5]
However, none of these cases involve OpenCase as the cited tool, and there is no reporting in the provided results about an April 2026 incident matching your headline.
To properly research this story, you would need current search results from April 2026 or more recent legal databases covering recent attorney sanctions and AI-related misconduct allegations.