Blurred Lines: When Fact Witnesses Offer Expert Opinions

By Noah Bolmer

The criminal trials of Elizabeth Holmes and Ramesh “Sunny” Balwani, former executives of Theranos, provide a case study in the use of expert testimony in complex white-collar litigation. Both defendants faced federal charges of wire fraud and conspiracy for allegedly misleading investors and patients about the capabilities of Theranos’s blood-testing technology.  

Although they were indicted together, the court severed the cases, resulting in two separate trials: Holmes’s trial ran from August 2021 to January 2022, and Balwani’s from March to July 2022. Here, we focus on the Holmes trial and the joint appeal where several fact witnesses were found to have been acting as expert witnesses.  

Background 

Theranos claimed to revolutionize diagnostic testing by using its proprietary “Edison” devices to run a wide range of laboratory tests from just a few drops of blood. The technology was marketed as faster, cheaper, and less invasive than traditional venous draws, with the potential to disrupt the industry. Prosecutors alleged that these claims were knowingly false and that the devices were incapable of producing reliable results. Holmes and Balwani were accused of perpetuating this deception to secure hundreds of millions of dollars in investments and commercial partnerships. 

The Elizabeth Holmes Trial 

Expert testimony played a focused but critical role in the criminal trial of Elizabeth Holmes. The prosecution called Dr. Stephen Master, a clinical pathologist, to evaluate the reliability of Theranos’s blood-testing technology against accepted laboratory standards. His analysis helped translate complex scientific data into terms the jury could understand, grounding the case in objective measures of accuracy and precision. While other witnesses described technical failures from firsthand experience, Master’s expert perspective provided the trial’s clearest scientific assessment of Theranos’s core claims. 

Dr. Master was the only expert formally qualified under Rule 702 to testify in the criminal trial of Holmes. Retained by the U.S. Attorney’s Office, Master was tasked with evaluating whether Theranos’s blood-testing technology met accepted standards of clinical laboratory practice. His testimony focused on the performance of Theranos’s fingerstick assays, particularly their accuracy, precision, and compliance with regulatory norms.  

Testimony: Dr. Master 

During direct examination, Master explained the foundational principles of laboratory testing to the jury. “Accuracy,” he said, “refers to how close the result comes to the true amount of the analyte in a blood sample,” while “precision refers to the degree to which a test produces the same result when it measures the same sample multiple times”. He emphasized that both are essential for clinical reliability. Master reviewed Theranos’s internal validation documents, CMS inspection findings, and customer complaints, concluding that the company’s assays did not meet acceptable standards. He testified that Theranos, “did not adhere to normal industry standards for clinical laboratory testing from 2013–2015,” and that running patient samples when quality control values were out of range, “directly impact[s] the accuracy and reliability of the results that are returned to the patient or clinician.” 

On cross-examination, Holmes’s defense team sought to undermine Master’s conclusions by pointing out that he had never worked with Theranos’s proprietary devices and had not personally observed their operation. Creating distance between the expert and the facts of the case is a common tactic during cross. The opposing counsel’s goal is to suggest to the jury that the expert’s opinions are merely theoretical or based on incomplete information.  

Master acknowledged that he had not handled the instruments himself but maintained that his analysis was consistent with how clinical laboratorians evaluate assay performance. “Even without physically seeing an instrument,” he wrote in his supplemental report, “such documents allow me to determine, in my own practice of laboratory medicine, whether an assay meets appropriate criteria.” 

Impact: Dr. Stephen Master 

Master’s testimony was pivotal. By grounding his analysis in established laboratory metrics and regulatory expectations, he helped the jury understand why Theranos’ tests were not merely flawed but potentially dangerous. His expert opinion provided a scientific anchor for the prosecution’s broader narrative of deception and risk. In a trial filled with conflicting accounts and complex technology, Master’s testimony stood out for its clarity and rigor. 

The Verdict and Appeal 

Elizabeth Holmes was convicted on four counts of wire fraud and conspiracy to commit wire fraud, all related to misrepresentations made to Theranos investors. She was acquitted on charges involving patient harm, and the jury deadlocked on several others. After a lengthy trial, she was sentenced to 135 months in prison and would eventually (along with Balwani) be ordered to pay $452 million in restitution to defrauded investors. 

Holmes appealed her conviction to the Ninth Circuit, raising multiple challenges to the district court’s evidentiary rulings. Among them was the argument that certain witnesses—presented as fact witnesses—offered technical opinions that should have been subject to expert qualification under Rule 702. The appellate court addressed these claims in detail, setting the stage for a closer look at how courts distinguish between fact and expert testimony. 

The Rule 702 Controversy 

The Holmes and Balwani trials featured extensive testimony from individuals who had worked inside Theranos’s clinical labs. Two of the most consequential were Dr. Kingshuk Das and Dr. Mark Pandori, both of whom were presented as fact witnesses, yet their testimony included technical assessments that the Ninth Circuit later determined implicated 702. The court’s analysis of their roles offers a cautionary example of how expert opinion can enter the record without proper qualification, and how courts may respond on appeal. 

Background 

Dr. Kingshuk Das was Theranos’s final lab director, hired in late 2015 and remaining until the company’s collapse in 2018. A pathologist by training, Das was brought in during the company’s regulatory crisis and tasked primarily with responding to government audits and addressing lab deficiencies. His tenure coincided with Theranos’s shift away from its proprietary Edison devices, which he deemed unreliable. Das voided thousands of test results from 2014 and 2015, citing concerns about accuracy and patient safety.  

Dr. Mark Pandori served as co-lab director at Theranos from December 2013 to May 2014, during the period when the company launched patient testing at a pharmacy chain. He resigned after requesting that Holmes consult with lab directors before making public claims about the technology’s capabilities—a request that was rejected by Holmes’s partner, Sunny Balwani.  

Unqualified Expert Testimony 

Das’s conclusions about the Edison device’s clinical unsuitability and his decision to void thousands of test results were presented as factual recounting of his role. However, the Ninth Circuit found that these were not mere observations but technical judgments requiring expert qualification. His analysis relied on specialized knowledge and post-hoc evaluation of data, which placed it squarely within the scope of Rule 702. The appellate court noted that the district court erred in admitting this testimony without vetting Das as an expert. 

Pandori’s testimony followed a similar trajectory. He described proficiency testing procedures and compared Theranos’s results to those from third-party analyzers. While framed as a description of lab operations, the court found that his testimony involved evaluative judgments about accuracy and reliability to be within expert territory. The Ninth Circuit concluded that both witnesses had offered expert opinions under the guise of fact testimony. 

The Ninth Circuit’s Ruling 

In February of 2025, the court held that the district judge should have applied Rule 702 to assess the admissibility of these opinions. It acknowledged the procedural error but deemed it harmless, finding that the improperly admitted testimony did not affect the outcome of the trial. This harmless error doctrine, while preserving the verdict, leaves unresolved the broader issue of how courts should handle hybrid witnesses whose roles blur the line between fact and expert. This ruling has proven controversial.  

Implications 

For expert witnesses, the Holmes case serves as a cautionary example. The distinction between fact and expert testimony is not always controlled by how the witness is introduced or labeled. Courts may retroactively reclassify testimony based on its content, and failure to undergo proper qualification can raise appellate issues—even if the verdict stands. Experts who testify based on direct involvement must be prepared for their statements to be scrutinized under Rule 702, regardless of whether they are formally designated as experts. 

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