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Ramesh 'Sunny' Balwani, former president and chief operating officer of Theranos, leaves the courthouse in San Jose, Calif., on June 28.BRITTANY HOSEA-SMALL/Reuters

A jury on Thursday convicted former Theranos executive Ramesh “Sunny” Balwani of collaborating with disgraced Theranos CEO Elizabeth Holmes in a massive fraud involving the blood-testing company that once enthralled Silicon Valley.

The 12 jurors found Mr. Balwani guilty on all 12 felony counts of defrauding both Theranos investors and the patients who relied on wildly unreliable blood tests that could have jeopardized their health.

Mr. Balwani sat impassively as the verdicts were read, blinking frequently.

The outcome puts Mr. Balwani and Ms. Holmes in similar situations. Ms. Holmes was convicted on four counts of investor fraud and conspiracy earlier this year. During that trial, Ms. Holmes tearfully accused Mr. Balwani of sexually emotionally abusing her while they were lovers. An attorney for Mr. Balwani has vehemently denied those charges.

Both Ms. Holmes, 38, and Mr. Balwani, 57, face up to 20 years in prison.

Ms. Holmes is scheduled to be sentenced in late September. The date of Mr. Balwani’s sentencing is expected to be set in the coming days.

The dual convictions represent a resounding victory for federal prosecutors, who seized on the Theranos case as a rare opportunity to hold ambitious entrepreneurs accountable for engaging in technological hyperbole while pursuing fame and fortune. In the process, they hoped to discourage the practice of making bold and unproven promises about still-nascent products – a startup strategy known as “fake it until you make it.”

After the verdicts were read and the jury was dismissed, Mr. Balwani walked over to his two brothers who were sitting behind him for what appeared to be a solemn discussion. The three sat quietly, heads bowed.

While Ms. Holmes insinuated during her trial that Mr. Balwani manipulated her into making poor choices, Mr. Balwani’s lawyers explicitly sought to shift all the blame for any misconduct squarely on Ms. Holmes.

As part of Mr. Balwani’s defence, the lawyers pointed out that Ms. Holmes was not only CEO, but also a Silicon Valley star who persuaded investors to pour nearly $1-billion into Theranos. Ms. Holmes boasted that her company had found a way to scan for hundreds of potential diseases with a device called the Edison that could test just a few drops of blood taken with a finger prick. Such technology could potentially revolutionize health care.

But it turned out that the Edison never worked properly, providing faulty test results that Theranos conducted as part of a deal to set up mini labs in Walgreen’s pharmacies. The flaws in Theranos’ vaunted technology prompted Ms. Holmes and Mr. Balwani to shift their testing to conventional machines made by other vendors and while drawing vials of blood from patients’ veins – a far cry from Ms. Holmes’ promises.

After committing about $15-million of his own money to bolster Theranos and then becoming the company’s chief operating officer in 2010, Mr. Balwani eventually oversaw the blood-testing lab that was delivering the inaccurate results and supervised the Walgreen’s deal.

Unlike Ms. Holmes, who spent seven days on the witness stand during her trial, Mr. Balwani didn’t testify in his own defence.

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