Theranos founder Elizabeth Holmes has been convicted of defrauding investors after a months-long landmark trial in California.
Prosecutors said Holmes knowingly lied about technology she said could detect diseases with a few drops of blood.
Jurors found Holmes guilty of four charges, including conspiracy to commit fraud against investors and three counts of wire fraud.
She denied the charges, which carry a maximum prison term of 20 years each.
Holmes was not taken into custody, with no date confirmed yet for sentencing and a further hearing scheduled next week.
She faced 11 charges in total and was found not guilty of four charges relating to defrauding the public.
The split verdict came after the judge said the jury, having deliberated for seven days, could deliver a partial verdict after being unable to reach consensus on another three counts.
Theranos, at one point valued at $9bn (£6.5bn), was once the darling of Silicon Valley.
The firm promised it would revolutionise the healthcare industry, but its claims began to unravel in 2015 after a Wall Street Journal investigation reported that its core blood-testing technology did not work.
For nearly four months at trial, the jury of eight men and four women were presented with two starkly different accounts of the former self-made billionaire, whose downfall shook Silicon Valley.