Mystery surrounds Ramesh Balwani, the former right-hand man and ex-boyfriend of Theranos chief executive Elizabeth Holmes.
Holmes was convicted in the US on Monday of defrauding investors in her blood-testing start-up. The high-profile case is being viewed as an indictment of Silicon Valley culture.
In her testimony, the fallen US biotech mogul accused Mr Balwani of being abusive.
Who is Ramesh Balwani?
Mr Balwani got his start in software as a sales manager for Microsoft. From there, and from what little is known about him, he moved to the dot-com world in the early 1990s where he joined a company called CommerceBid.com.
CommerceBid.com, at which he was president, was a platform created to drive down the cost of suppliers by creating a bidding war. According to reports, the young company was quickly bought for $225 million by a rival: Commerce One. Commerce One eventually went public and was valued at almost $20 billion.
Just a few years later the company became a victim of the dot-com bubble and collapsed. According to reports at the time, Mr Balwani left the defunct business with almost $40m.
When did he meet Elizabeth Holmes?
Little is known about Mr Balwani in the years between the failure of Commerce One and his eventual connection with Elizabeth Holmes and Theranos. What is known is that the two met while Mr Balwani, then aged 37, was pursuing a master's degree in computer science at Stanford University. Mr Balwani is said to have dropped out of the programme in 2008.
In 2009, he joined Holmes's company as president, taking on the day-to-day running of the business. He later became chief operating officer and had a romantic relationship with Holmes, which has been detailed in emails submitted to the court.
What did Holmes say in her trial?
In her testimony, Holmes made graphic and disturbing allegations that Mr Balwani verbally and sexually abused her. Although these accusations are unlikely to play a part in his own trial, the conversations between Holmes and Mr Balwani are expected to play a major role in the government's case that the two were co-conspirators.
Mr Balwani faces fraud charges, with his case scheduled to go trial next year. He has pleaded not guilty.