A California federal magistrate judge on Wednesday warned attorneys representing Databricks in a group of writers' copyright lawsuit over AI training that they cannot discuss deposition testimony with witnesses during breaks other than for privilege reasons, but she rejected the writers' accusation that defense counsel had improperly coached witnesses.

The discovery ruling is the latest development in a high-stakes proposed class action filed in March 2024 by writers Abdi Nazemian, Brian Keene and Stewart O'Nan who allege their books were part of a pirated database that Databricks and its subsidiary, MosaicML, used to train large language models without consent or compensation. Databricks acquired MosaicML for roughly $1.3 billion in 2023.

In a joint letter last week, the writers accused defense attorneys of coaching two witnesses, MosaicML co-founder Hanlin Tang and former MosaicML chief scientist Jonathan Frankle, during depositions, and improperly directing them not to answer certain questions. Both witnesses are now executives and researchers at Databricks.

Meanwhile, defense counsel countered that the plaintiffs should not be allowed to ask "personally invasive and harassing" questions.

U.S. Magistrate Judge Lisa J. Cisneros reviewed the witnesses' transcripts, and in a 5-page order on Wednesday, she denied the writers' request to further examine the witnesses.

Judge Cisneros agreed with the writers that Databricks' counsel improperly discussed the substance of the examinations with Tang and Frankle during deposition breaks, and she noted that the "far better course" would have been for defense counsel to examine the witnesses and show them certain documents "on the record during the deposition."

However, the judge said those witnesses did not change their testimony following their discussions with defense counsel, and the writers' counsel were still able to ask follow-up questions, so further questioning is not warranted.

Judge Cisneros additionally found that defense counsel improperly directed Tang not to answer certain questions during his deposition about how much he stood to gain from Databricks' acquisition of MosaicML purportedly due to defense counsel's privacy concerns.

The judge noted that Databricks' privacy concerns are "somewhat overblown," given that the depositions are sealed and the witness' personal stake in the MosaicML deal may be relevant to the writers' claims.

"The court notes that this does not give plaintiffs carte blanche to question witnesses regarding their personal finances unrelated to the acquisition or the financial benefit from defendants' alleged infringement, and instructions not to answer may be appropriate in such situations," the order adds.

Even so, the judge warned Databricks counsel that her standing order and the district's case law prohibits private conferences between deponents and attorneys "in the course of interrogation, including a line of related questions." The sole exception to that prohibition is to determine whether a privilege should be asserted, the judge said.

"If counsel believes that a witness's testimony requires clarification or needs to refresh the witness's recollection, the proper procedure is for them to question the witness 'on the record at the conclusion of the deposition' rather than confer with the witness during breaks," the order says. "Counsel shall comply with these procedures at any future depositions."

Judge Cisneros also noted that examining counsel can ask witnesses whether they discussed non-privileged testimony with their attorneys during breaks, and those witnesses are only required to confirm or deny whether they did without disclosing the content of their discussions or waiving attorney-client privilege.

Counsel and representatives for the parties did not immediately respond to requests for comment on Wednesday.

The proposed class is represented by Joseph R. Saveri, Christopher K.L. Young, Evan Creutz, Elissa A. Buchanan, William Castillo Guardado and Jane J. Kim of the Joseph Saveri Law Firm LLP, Justin A. Nelson, Alejandra C. Salinas, Rohit D. Nath, Elisha Barron, Craig Smyser, Jordan W. Connors and Trevor D. Nystrom of Susman Godfrey LLP, Rachel J. Geman, Danna Z. Elmasry, Anne B. Shaver and Betsy A. Sugar of Lieff Cabraser Heimann & Bernstein LLP, Bryan L. Clobes, Alexander J. Sweatman and Mohammed A. Rathur of Cafferty Clobes Meriwether & Sprengel LLP, Brian D. Clark, Laura M. Matson and Arielle Wagner of Lockridge Grindal Nauen PLLP, and Matthew Butterick.

Databricks and Mosaic are represented by Jedediah Wakefield, Brian David Buckley, Charles Moulins, David Lloyd Hayes, Deena Julia Greenberg Feit, Diana Buck, Justine Alexis Vandermel, Ryan Kwock and Zachary Harned of Fenwick & West LLP.

The case is In re: Mosaic LLM Litigation, case number 3:24-cv-01451, in the U.S. District Court for the Northern District of California.