The verdict for Ramesh Balwani, who helped lead the failed blood testing start-up, was more severe than the one for his ex-girlfriend Elizabeth Holmes.

SAN JOSE, Calif. — Ramesh Balwani, a former top executive at Theranos, was found guilty on Thursday of 12 counts of fraud, in a verdict that was more severe than that of his co-conspirator, Elizabeth Holmes, and that solidified the failed blood-testing start-up as the ultimate Silicon Valley cautionary tale.

Mr. Balwani and Ms. Holmes, who together pushed Theranos to soaring heights with a promise to revolutionize health care, are the most prominent tech executives to be charged with and convicted of fraud in a generation. A jury of five men and seven women took 32 hours to produce a verdict, convicting Mr. Balwani, known as Sunny, of all 10 counts of wire fraud and two counts of conspiracy to commit wire fraud.

Ms. Holmes was convicted in January on four counts of fraud and acquitted of four counts of fraud. Three other charges were dismissed after the jury could not reach a consensus. She has appealed the verdict, and Mr. Balwani is expected to do the same

Both of their cases hinged on whether they had exaggerated the abilities of Theranos’s blood-testing machines in order to appeal to investors and customers, when the products did not actually work.

Each count carries a maximum sentence of 20 years in prison. Ms. Holmes is expected to be sentenced in September, and Mr. Balwani in November.

As the guilty verdicts rolled in, Mr. Balwani, 57, who appeared in court in a black suit and a blue medical mask, briefly shot a look at the jury before fixing his gaze straight ahead. One of his lawyers, Jeffrey Coopersmith, said in a statement that his team was “obviously disappointed” by the verdicts and that Mr. Balwani would consider all of his options, including appeal.

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In a prepared statement delivered outside the courtroom, Stephanie Hinds, a U.S. attorney, said her office appreciated the verdict, and she thanked the jury for “dutifully navigating through the complex issues presented by this case.”

The dual guilty verdicts are a rare instance of the Silicon Valley hype machine leading to possible prison time. Since Theranos collapsed in 2018, the company has become a form of shorthand for business grifters, and the world has developed a voracious appetite for messy start-up rise-and-fall stories, such as WeWork’s disastrous first attempt to go public and the trickery of Ozy Media. But Theranos was the only one to result in criminal charges. The consequences its executives have faced are likely to send a message to entrepreneurs who exaggerate in the name of innovation.