The fraud conviction of former Theranos CEO Elizabeth Holmes could do more than just send a once-celebrated billionaire to prison for years.

Former U.S. Secretary of Defense James Mattis testified Wednesday in the trial of fallen tech star Elizabeth Holmes, saying the entrepreneur misled him into believing she was on the verge of rolling out a blood-testing breakthrough that he hoped would help save lives of troops in battle.

Elizabeth Holmes once seemed destined to fulfill her dream of becoming Silicon Valley's next superstar.

Jury selection in the fraud trial of Theranos founder Elizabeth Holmes began Tuesday, casting a spotlight on the fallen Silicon Valley star now facing felony charges alleging she duped elite financial backers, customers and patients into believing that her startup was about to revolutionize medicine.