Disgraced Silicon Valley star and Theranos CEO Elizabeth Holmes unexpectedly took the witness stand, a move that carries considerable risk, late on Friday at her criminal trial for fraud.

The disgraced CEO — who has been accused of deceiving investors and patients about her blood-testing startup Theranos and is facing charges of fraud and conspiracy — surprisingly took the stand on Friday, according to a report by Associated Press.

Holmes’ attorney Kevin Downey told U.S. District Judge Edward Davila that he expects the Theranos CEO to continue her testimony on Monday and Tuesday. Prosecutors, however, aren’t likely to cross-examine Holmes until after the Thanksgiving holiday weekend.

Elizabeth Holmes, CEO of Theranos, participates in the closing plenary session of the Clinton Global Initiative 2015 Annual Meeting at the Sheraton New York Times Square Hotel, on Tuesday, Sept. 29, 2015 in New York. (Photo by Greg Allen/Invision/AP)

Prosecutors have already called 29 witnesses to the stand to support their claim that Holmes endangered patients’ lives while also swindling investors and customers about Theranos’ technology.

They also presented internal documents and salacious texts between Holmes and her ex-boyfriend and former Theranos chief operating officer (COO) Ramesh “Sunny” Balwani, who is also facing charges of wire fraud and conspiracy.

Texts between Holmes and Balwani revealed the disgraced CEO boasted that she was the “best businessperson of the year,” just a year before the company fell apart amidst allegations of widespread fraud.

Court documents show that Holmes’ attorneys assert she was manipulated by Balwani through “intimate partner abuse.”

While on the stand, Holmes began her testimony by recounting her early years as a student at Stanford University, and her interest in disease detection, which led to her decision to drop out of school in 2003 at the age of 19 to found the startup that eventually became Theranos.

Holmes said she convinced her parents to let her use her college savings to finance her ambitions.

“I started working all the time — trying to meet people who could help me could build this,” she said.

Theranos eventually developed a device called the Edison, which allegedly needed only a few drops of blood to scan for hundreds of health problems. Current tests generally each require a vial of blood, making it both slow and impractical to run more than a handful of patient tests at a time, notes AP.

Had it worked as promised, the Edison could have revolutionized health care by making it easier and cheaper to scan for early signs of disease and other health issues, the report adds.

Holmes boasted to investors about the alleged breakthroughs, which were later proved to be untrue, according to recordings presented during the trial.

Witness testimony and other evidence strongly suggested that the CEO misrepresented purported deals with major pharmaceutical companies, such as Pfizer and the U.S. military, while also concealing hiding problems with the Edison.

By 2015, Holmes and Balwani had reportedly raised hundreds of millions of dollars from investors — such as media mogul Rupert Murdoch and the Walton family of Walmart — and struck deals with Walgreens and Safeway to conduct blood tests in their pharmacies.

At one point, those investments valued Theranos at $9 billion, which gave Holmes a $4.5 billion fortune on paper by 2014.

Holmes also allegedly distributed financial projections calling for Theranos to generate $140 million in revenue in 2014 and $990 million in revenue in 2015 while also turning a profit, according to evidence presented at the trial.

But a copy of Theranos’ 2015 tax return showed the company had revenues of less than $500,000 that year while reporting accumulated losses of $585 million.

If convicted, Holmes, now 37, could be sentenced to up to 20 years in prison.

You can follow Alana Mastrangelo on Facebook and Twitter at @ARmastrangelo, and on Instagram.