Elizabeth Holmes found guilty of four counts of fraud.

The founder of the failed blood testing start-up Theranos was found guilty of four charges of fraud on Monday, in a case that came to symbolize the pitfalls of Silicon Valley's culture of hustle, hype and greed.

Ms.Holmes was the most prominent tech executive to be accused of fraud in a generation of high-flying, money-losing start-ups. A jury of eight men and four women took 50 hours to reach a verdict, convicting her of three counts of wire fraud and one count of conspiracy to commit wire fraud. She was found not guilty on four other counts.

Each count carries a maximum sentence of 20 years in prison, terms that are likely to be served concurrently. Ms.Holmes is expected to appeal.

The verdict is rare. Few technology executives are charged with fraud. Martha Stewart was sentenced to prison in 2004 for lying to investigators about a stock sale. Silicon Valley start-ups that stretch the truth to score funding and business deals are likely to be warned by Theranos.

The jury believed the evidence presented by the prosecutors that Ms.Holmes lied about her work at Theranos. They were not swayed by her defense of blaming others for Theranos's problems and accusing her co-conspirator, the company's chief operating officer, of abusing her.

The guilty verdict arrived in a frenzied period for the tech industry, with investors fighting to get into hot deals and often ignoring potential red flags about the companies they were putting money into. There are people who warn that there will be more Theranos-like disasters.