Theranos founder Elizabeth Holmes has been found guilty of conspiring to defraud investors.
A jury in California found Holmes guilty on four of 11 counts, including conspiracy to commit fraud against investors and three counts of wire fraud.
Holmes was accused of knowingly misleading investors over her blood testing start up, lying that her technology could identify diseases from just a few drops of blood.
The 37-year-old had pleaded not guilty in the landmark trial, with the charges carrying a maximum prison term of 20 years each.
The Silicon Valley boss had an estimated net worth of $4.5bn in 2015, according to Forbes, after founding Theranos in 2003.
A sentencing date has not yet been confirmed while a further hearing is scheduled for next week.
Holmes was acquitted on three counts of defrauding patients who paid for tests from Theranos, and a related conspiracy charge. The jury failed to reach a decision on three counts related to individual investors, after deliberating for seven days.
During the months-long trial, the prosecution argued Holmes was fully aware she was selling an investors a false idea but was fuelled by ambition for the firm’s success.
Multiple lab directors testified to say they were instructed by the businesswoman to downplay their concerns over flaws in the firm’s technology.
Holmes was accused of choosing fraud “over business failure,” by prosecutor Jeff Schenk. “She chose to be dishonest with investors and patients. That choice was not only callous, it was criminal,” he said.
The defence had argued Holmes was a dedicated entrepreneur, having founded her firm at the young age of 19, and never knowingly defrauded any parties.
Testifying in her own defence, Holmes accused Ramesh Balwani, her former business partner and boyfriend, of emotional and sexual abuse. Balwani denies these allegations.