Katherine Trefz

Katherine Trefz represented Elizabeth Holmes, examining witnesses about patient-test evidence, message records, and the limits of their personal or technical knowledge. She also presented defense evidence about Theranos records and its later technology and regulatory work.

Trefz cross-examined Audra Zachman on her review of Brittany Gould's conflicting HCG results and Theranos's corrective response; Zachman maintained that Gould’s result remained unusual. With Erin Tompkins, Trefz tested recollection and interpretation of differing HIV results while the court limited questions lacking medical foundation. She questioned Mark Burnes about possible laboratory error in a patient's PSA result; he said significant PSA errors were rare.

On digital and financial records, Trefz established through Justin Offen that matching message timestamps did not prove which message was viewed first. Roberto Amenta acknowledged that retrieving wire records gave him no personal knowledge of why the transfers were made or authorized. Trefz also sought more context for Holmes-Balwani messages under Rule 106; the court admitted some proposed additions and excluded others for lack of foundation.

During the defense case, Trefz presented Trent Middleton's summaries of patent, financial, investment, test-menu, and laboratory records, subject to limits on admissibility. She examined Fabrizio Bonanni about the later Minilab, board discussions, and quality and compliance reforms. On redirect, she established that he had not independently reviewed an earlier decision to void test results.