Elizabeth Holmes says she had faith in Theranos?s early studies

The Theranos founder Elizabeth Holmes completed a second day of testimony in her own defense, in a widely followed fraud trial that could have major implications for Silicon Valley.

Flanked by her mother and partner Billy Evans, Holmes brusquely walked into the federal courthouse in San Jose, California, past throngs of journalists who had been waiting since the early morning hours to chronicle one of the most high-profile trials the tech world has seen in decades.

She faces up to 20 years in prison for allegedly defrauding investors and patients after her company's blood-testing devices failed to deliver on ambitious promises to perform hundreds of health tests using just a drop of blood. Holmes, 37, has pleaded not guilty.

In her testimony on Monday, Holmes primarily focused on her understanding at the time that Theranos's technology was more accurate than it was due to the company's early trials.

The defense introduced studies of Theranos's blood-testing machines that showed favorable results for the company, including research from big-name pharmaceutical firms such as Pfizer, Novartis and AstraZeneca. Holmes said she took the studies to mean the devices had been vetted.

One study, conducted by Stanford University, concluded the blood devices had found "very clear patterns of disease progression, remission and effects of therapies are apparent".

Holmes said that at the time the numbers meant "our system was working well". Other studies referenced by the defense included one conducted by Schering-Plough (a pharmaceutical firm that later became Merck) and Pfizer.