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SAN JOSE, Calif. — For more than three months, the defendant has donned a medical…

SAN JOSE, Calif. — For more than three months, the defendant has donned a medical mask, clutched arms with her mother and entered the Robert F. Peckham Federal Building in San Jose, Calif., where executives, scientists and investors have accused her of fraud.

Now a jury of strangers will decide on her guilt.

A jury of eight men and four women were handed the case late Friday of Elizabeth Holmes, the founder of the blood testing start-up Theranos. Lawyers for both sides finished their closing arguments earlier in the day in the nearly four-month-long trial and Judge Edward J. Davila of U.S. District Court for the Northern District of California read detailed instructions to the jury. Jurors will meet to deliberate on Monday morning.

In the courtroom on Friday morning, Kevin Downey, a lawyer for Ms. Holmes, spent nearly three hours attempting to discredit each of the government’s witnesses and raise doubt in jurors’ minds. As he flipped through slides meant to dismantle the prosecution’s evidence with headings including “Not every potential issue is an actual issue,” a few jurors scribbled notes.

Mr. Downey concluded by saying Ms. Holmes was not a criminal. “She believed she was building a technology that would change the world,” he said, raising his voice and gesturing dramatically.

Ms. Holmes faces 11 charges of wire fraud and conspiracy to commit wire fraud for claims she made to investors and patients about Theranos’s technology and business dealings. She has pleaded not guilty. If convicted, she faces up to 20 years in prison.

The trial, which has alternated between media spectacle and business-school cautionary tale, has come to represent a moment of truth in Silicon Valley, where executives have rarely faced consequences for their inflated claims. If Ms. Holmes is found guilty, prosecutors could begin to more aggressively dig into the wildly optimistic tales of rocket ship growth at more start-ups.

Even if she is acquitted, some executives may still tread more carefully in their optimistic pitches. Start-ups have been riding a wave of investor exuberance for nearly a decade, despite repeated warnings of bubble-like behavior that could lead to more disasters like Theranos.

“I would suspect that C.E.O.s of similar companies will be more careful when they talk,” said Andrey Spektor, a lawyer at Bryan Cave Leighton Paisner and a former federal prosecutor in New York’s Eastern District. He said recordings of Ms. Holmes pitching her company to investors and on TV were among the most incriminating evidence in the case.

Prosecutors used dozens of witnesses and hundreds of documents to argue that Ms. Holmes, 37, knowingly lied to investors about Theranos. She said the company had military contracts when it did not, that its technology was “comprehensively validated” by pharmaceutical companies when it had not been, and that its machines could do hundreds of tests when it could only do a dozen.

On Thursday, Jeff Schenk, an assistant U.S. attorney and one of the lead prosecutors, summarized the government’s case simply: When Theranos was almost out of money, Ms. Holmes could have let it fail. But she chose to defraud investors instead, he said.

“That choice was not only callous, it was criminal,” Mr. Schenk said.

Ms. Holmes’s lawyers countered with a range of responses: She had been told by her colleagues that the technology worked, she had hid information to protect trade secrets, she had moved to fix the problems once she learned of them, and the broader narrative about Theranos was more complicated than the prosecution had made it seem.

“The government is showing an event that looks bad, but at the end of the day, when all the evidence flows together, it isn’t so bad,” said Mr. Downey. He showed slides illustrating the steep burden of the government to prove “beyond reasonable doubt” that Ms. Holmes had knowingly lied to get money.

Ms. Holmes’s defense primarily relied on her own testimony, which lasted seven days and upended the narrative of the case. It was the first time that Ms. Holmes had told her version of the events leading to Theranos’s collapse, which has been widely documented in podcasts, books, documentaries and news reports.

On the stand, Ms. Holmes painted herself as a hardworking and ambitious entrepreneur who believed in her company’s technology and potential. Any exaggerations or misleading statements were merely her projecting grand plans for the future, she implied.

She further said Ramesh Balwani, her former longtime boyfriend and business partner, who is known as Sunny, had berated her and controlled every aspect of her life. She also accused him of sexual abuse, which he has denied. Their relationship had been kept a secret at the time.

But in court, every aspect of the relationship — text messages, emails, conversations, infidelities and the limited liability company through which they owned a home — was picked apart. Prosecutors dug in to try to show the pair conspired to commit fraud. Ms. Holmes’s lawyers tried to show she was a victim.

It is rare for defendants in white-collar criminal trials to take the stand, and it is even rarer for them to introduce testimony of abuse. Ms. Holmes’s lawyers were expected to call an expert witness to tie her claims of intimate partner abuse to the alleged fraud, but they did not.

On Friday, John Bostic, a prosecutor, elaborated on statements made by Mr. Schenk the day before about the abuse allegations, telling the jury they did not need to come to any conclusion about Ms. Holmes and Mr. Balwani’s relationship to issue a verdict. He also attempted to separate the abuse from the fraud charges.

“There is no evidence regarding a link between what their relationship was like and the conduct she is charged with committing,” he said.

Ms. Holmes’s testimony added to the spectacle of the trial, drawing large crowds of onlookers who often waited more than five hours outside the courtroom for one of its limited seats. One man yelled that Ms. Holmes was a “girl boss” as she entered the building, and a trio of attendees pretended to sell black turtlenecks — Ms. Holmes’s business uniform during Theranos’s rise — as part of a performance art piece.

On Friday, Mr. Downey closed his argument by saying that Ms. Holmes did not intentionally defraud anyone. When Theranos got into trouble, he said, Ms. Holmes did not try to cover up, cash out or flee like a criminal would.

“She went down with that ship,” he said.

Mr. Bostic rebutted Mr. Downey by reiterating the government’s argument against Ms. Holmes.

“The disease that plagued Theranos wasn’t a lack of effort,” he said. “It was a lack of honesty.”