One of the biggest Silicon Valley spectacles since the introduction of the iPhone was the trial of ElizabethHolmes, a starentrepreneur who defrauded investors in her blood-testing start-up. A chief executive was held criminally responsible for lying when she was convicted in January.

For much of her trial, Ms. Holmes tried to blame her deputy and former boyfriend for what went wrong at her company. Mr. Balwani will be able to respond in his own fraud trial. The same federal courtroom in San Jose, Calif., where Ms. Holmes's fate was decided, was to be used for jury selection on Wednesday.

A close examination of an unusual relationship between a young woman and an older man is promised in the first trial and the second trial. Ms. Holmes and Mr. Balwani had a secret romance that was also a professional alliance, an exciting promise to improve health care for millions that instead put patients at risk. Even though they thought new and better technology would save them from their reckless claims, their blood testing didn't work.

Mr. Balwani was a software executive who made a fortune during the dot-com boom. He befriended her when they were studying in China. Their romantic relationship eventually led him to join Theranos as president and chief operating officer.

He wasn't mentioned in the glowing cover stories about Ms. Holmes and Theranos. The start-up was ruled by a team that included Mr. Balwani and Ms. Holmes. Few knew they were in a relationship.

Reed Kathrein, a San Francisco lawyer who successfully sued Ms. Holmes and Theranos, said that she was the wizard of Oz, dazzling the investors and media, but he was the one behind the curtain working the machinery. He was confident that the prosecution would show that he knew she was lying and never stopped.

Mr. Kathrein said that he knew everything.

Mr. Balwani's trial will be familiar. He faces the same charges as before. The count was dropped because of a procedural error. He has denied the charges.

The jury couldn't reach a verdict on three investor counts, but they found her guilty on four counts of defrauding investors. She will be sentenced in the fall.

Elizabeth Holmes, center, with her mother, Noel, and partner, Billy Evans, during her trial.
ImageElizabeth Holmes, center, with her mother, Noel, and partner, Billy Evans, during her trial.
Elizabeth Holmes, center, with her mother, Noel, and partner, Billy Evans, during her trial.Credit...Jim Wilson/The New York Times

Legal experts agree that the government's successful prosecution of Ms. Holmes will give it a boost in Mr. Balwani's trial.

James Melendres, a former federal, said that the government has had the chance to do a full run.

Mr. Balwani and his lawyers did not comment. Through her lawyers, she didn't say anything.

Ms.Holmes' background has been extensively documented, but little is known about Mr. Balwani.

He had the good fortune to have his start-up purchased by a larger firm right before the 2000 stock market crash, which gave him about 40 million dollars. He got a divorce, went back to school to get an M.B.A., and bought fancy cars. His license plate was a nod to Karl Marx. His lawyers have said that he invested millions of his own money in the company.

He had a reputation for being a harsh, demanding boss who became increasingly paranoid that his employees would steal trade secrets that would supposedly change blood testing. The journalist John Carreyrou wrote about an incident in which Mr. Balwani called the police to chase after a departing employee.

Mr. Balwani's lawyers are expected to emphasize his lack of experience in medical devices, which was at the heart of Theranos's claims. Legal experts said he was not likely to testify. He would most likely be less sympathetic on the witness stand than Ms.Holmes, a new mother who played up her youth and arrived in court holding hands with her mother and her partner.

Ann Kim, a former federal prosecutor who represents companies undergoing government investigations, said that he doesn't have those niceties in his favor.

bombshell allegations of abuse against Mr. Balwani were introduced when Ms.Holmes took the stand in her defense. He denied the accusations, and text messages released during the trial depicted a relationship of more or less equals, as the company came under pressure from whistle-blowers and the media.

The whole thing that we have to respond to liars is ridiculous. Mr. Balwani promised to take legal action against their accusers.

The government's case is that both defendants stepped over the line from hype to deception.

The Apple co- founder Steve Jobs could be a good example of an alternate reality for Ms.Holmes. People testified that she made them believe she would change the world. There was nearly $1 billion invested into Theranos.

Mr. Balwani had no such gifts. There is only one online video of him.

Mr. Balwani gave a presentation on healthcare innovation to the Arizona Senate. He wasn't supposed to do it, and he didn't look like he was enjoying himself.

A Theranos Wellness Center inside a Walgreens pharmacy in Phoenix in 2016.
ImageA Theranos Wellness Center inside a Walgreens pharmacy in Phoenix in 2016.
A Theranos Wellness Center inside a Walgreens pharmacy in Phoenix in 2016.Credit...Steve Craft for The New York Times

The company was working on something that they believe is magic, and Mr. Balwani talked about a patient who had no limbs. He had a small limb attached to his body and we were able to do a finger test on him.

How a limbless person gained a limb was not explained. It was almost as if Mr. Balwani had dared the senators to point out that Theranos was magical thinking.

They did not. They saluted him.

"I love bringing the free market to our health care system and I was a family doctor," said State Senator Kelli Ward, a Republican.

The chair of the State Republican Party, Senator Ward, was involved in efforts to overturn local election results in favor of President Trump.

The prosecution and defense have not filed their final list of witnesses. Lawyers filed their proposed questionnaires for potential jurors in December.

The mother and former Secretary of State of Henry Kissinger were both struck from the trial. The expert witness on domestic abuse who did not take the stand was also removed. The legal team named experts on forensic accounting.

A potential witness for the government would make news. Even if she testifies, she is unlikely to reduce her prison sentence.

Jen Kennedy Park is a white-collar defense lawyer.