A US jury on Thursday convicted former Theranos President Ramesh "Sunny" Balwani of defrauding investors and patients about the blood-testing start-up that was once valued at $9 billion.
Balwani was convicted on two counts of conspiracy and 10 counts of fraud, a spokesman for the US Attorney's office confirmed.
A lawyer for Balwani did not immediately respond to a request for comment.
The jury in San Jose, California, handed down its verdict after deliberating for a little more than five days.
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Theranos's founder Elizabeth Holmes, who initially faced the same charges, was convicted on three counts of fraud and one count of conspiracy at a trial in January.
Balwani and Holmes were charged in 2018 with lying to investors about the company's finances and its machines' ability to run a broad range of tests from a few drops of blood.
Prosecutors also charged the pair with duping patients about the tests' accuracy.
They were granted separate trials after Holmes said she would testify that Balwani was abusive towards her in their romantic relationship. Balwani has denied the allegations.
Theranos investors were drawn to Holmes, with her deep voice and black Steve Jobs-type turtleneck, and her promise to upend the lab testing industry by creating portable machines that could run a broad range of tests.
The company promoted work with drug makers, pharmacies and the US military, and received investments from Rupert Murdoch, to name a few.
Theranos collapsed after The Wall Street Journal published articles, starting in 2015, that suggested its devices were flawed and inaccurate.
At trial, Holmes made the unusual decision to testify in her own defence and denied lying to investors.
She is due to be sentenced on September 26 and has said that the evidence was insufficient to support the verdict.