The founder of Theranos, a US company that claimed it provided revolutionary blood tests, has been found guilty of four counts of fraud.

Jurors in the US found Elizabeth Holmes guilty of one count of conspiracy to commit fraud against investors and three counts of wire fraud following a 15-week trial.

Holmes, who faces a maximum of 20 years in prison, denied the charges and was found not guilty of four charges relating to defrauding the public.

The 37-year-old founded Theranos in 2003, with the company claiming to have technology that could run multiple tests on a raindrop-sized pinprick blood sample, rather than the multiple vials usually required. The company was once worth around £6.9 billion ($9 billion) and employed 800 people.

Holmes claimed Theranos had developed an analyser, variously referred to as the Theranos Sample Processing Unit (TSPU), Edison, or minilab.

She claimed this analyser was able to perform a full range of clinical tests using small blood samples drawn from a finger stick and could produce results that were more accurate and reliable than those yielded by conventional methods—all at a faster speed than previously possible. However in 2015, a Wall Street Journal investigation questioned the blood-testing technology.

The trial included evidence which claimed Holmes knowingly made materially false representations to investors and potential investors about the analyser. This included evidence which demonstrated that Holmes knew the analyser had accuracy and reliability problems, performed a limited number of tests, was slower than some competing devices, and, in some respects, could not compete with existing, more conventional machines. Evidence also showed that Holmes resorted to using conventional machines bought from third parties to perform much of Theranos’s blood testing.

While the prosecution sought to prove that Holmes knew about the deception surrounding Theranos’ technology, Holmes maintained that she never knowingly defrauded patients or investors.

Following the verdict, Holmes was not taken into custody and no date has been confirmed for sentencing, though a further hearing is scheduled for next week.