Elizabeth Holmes Takes the Stand in Criminal-Fraud Trial

SAN JOSE, Calif.—Elizabeth Holmes took the witness stand Friday afternoon to defend herself against criminal-fraud charges tied to the failure of Theranos Inc., the startup she founded in 2003 as a 19-year-old college dropout.

Ms. Holmes, who appeared composed and polished, opened her testimony at the beginning of the Theranos story: discussing her laboratory work as a college freshman at Stanford University, the mentorship she received from a Stanford professor and her vision even as a teenager to change healthcare. Her appearance—unmasked for the first time in court—energized a case that is heading toward its 12th week of testimony.