SAN JOSE, Calif.—Jurors heard testimony this week from voices that have been scant in Elizabeth Holmes’s criminal-fraud trial so far: patients who took Theranos Inc. tests, as well as Ms. Holmes herself.

The patient testimony from two Arizonans who received troubling test results addresses a crucial element of the government’s case against Ms. Holmes, backing several wire-fraud counts and one conspiracy count that charge her with misleading patients about the capabilities of Theranos’s blood-testing technology.

Roger...

SAN JOSE, Calif.—Jurors heard testimony this week from voices that have been scant in Elizabeth Holmes’s criminal-fraud trial so far: patients who took Theranos Inc. tests, as well as Ms. Holmes herself.

The patient testimony from two Arizonans who received troubling test results addresses a crucial element of the government’s case against Ms. Holmes, backing several wire-fraud counts and one conspiracy count that charge her with misleading patients about the capabilities of Theranos’s blood-testing technology.

Roger Parloff, a journalist for Fortune who wrote a profile of Ms. Holmes in 2014 that was later retracted, also took the stand Thursday afternoon as the government wound down its case in the closely watched Silicon Valley trial. Ms. Holmes had widely shared that article with investors. Jurors heard audio clips of Ms. Holmes in recorded conversations she had with Mr. Parloff during his reporting process, including one in which Ms. Holmes talks about several “quite promising” possible uses of Theranos’s technology by the military. “That’s something personally I’m very passionate about,” Ms. Holmes said.

Although patients form the basis for nearly half the charges against Ms. Holmes, their testimony has been sparse. An order from U.S. District Judge Edward Davila ahead of the trial severely limited the scope of what patients could say to the facts around the tests they received, giving them a quick turn on the stand. But even with those limitations, their testimony about their experience getting alarming information about serious health conditions could elicit sympathy from the jury, helping prosecutors in their case.

The story of patient Mehrl Ellsworth was told in court mostly through his doctor, Mark Burnes, who has an internal-medicine practice in Arizona and ordered the Theranos tests. Dr. Burnes testified Thursday about the Theranos lab results he received for Dr. Ellsworth, a retired dentist who also spoke to The Wall Street Journal this summer about his experience with the blood-testing company.

In May 2015, Dr. Ellsworth received a prostate-specific antigen test showing a result of 26.1, a result that was alarming, Dr. Burnes said from the stand. Such a high result can be an indication of prostate cancer.

Theranos ran a new test four days later, which showed a value of 1.71, more in line with a normal outcome. But tests repeated through Theranos the next month returned erratic results. Getting an accurate result was essential, because Dr. Ellsworth was preparing to leave the country for a few years for missionary work with the Church of Jesus Christ of Latter-day Saints and needed a clean bill of health, according to court testimony.

Dr. Burnes spoke with Theranos employees about the results, saying he suspected errors.

In the trial of Elizabeth Holmes, prosecutors have shown texts, emails and audio clips portraying her in her own words. WSJ’s Shelby Holliday asked reporter Sara Randazzo about key pieces of evidence and what to expect. Photo: Nick Otto/AFP via Getty Images The Wall Street Journal Interactive Edition

Jurors saw a series of internal Theranos emails discussing the problem and how to respond to Dr. Burnes. An entire email chain about Dr. Ellsworth’s results was forwarded to Ms. Holmes, jurors saw.

Dr. Ellsworth, who has a background in microbiology, told the Journal earlier this year he had always suspected the Theranos test results were wrong. He took the stand for mere minutes, to confirm the tests jurors had already seen were his.

Jurors also heard from patient Erin Tompkins, who testified on Wednesday about her experience taking a Theranos test at a Walgreens store in Arizona in May 2015.

Her test results, displayed in court, showed the detection of an HIV antibody. Three other HIV markers came back as not detected.

Ms. Tompkins said she called Theranos to ask to speak to someone in the lab about how these results were possible, because she had never been diagnosed with HIV or AIDS in the past. She testified she was told by a Theranos customer-service representative that she couldn’t be transferred to someone in the lab.

“And that was about it,” said Ms. Tompkins, who added: “I was quite emotional at the time.”

About three months later, she was able to get retested at another lab and all HIV-related tests came back negative. Three years later, she received another negative result.

Ms. Tompkins didn’t have insurance at the time and said Theranos’s low pricing was one of the things that appealed to her when she requested that her doctor send her to a Theranos lab.

Asked whether cost or accuracy were more important to her, Ms. Tompkins responded, “Well, I think accuracy is the most important any time you’re having a medical procedure.”

Mr. Parloff’s testimony summed up several themes of the prosecution’s case, as he recounted the claims about Theranos he was told during his reporting process, many of which jurors have since heard weren’t true.

Theranos showed him confidential reports claiming to be validation of the startup’s technology by two pharmaceutical companies, which earlier testimony showed were produced by Theranos without the companies’ knowledge.

In one audio clip played in court, Ms. Holmes tells Mr. Parloff that Theranos is capable of running tests for 1,000 different diagnostic codes, even beyond the 200 specific blood tests listed on the Theranos website. “We can handle it,” she says.

As the snippet winds down, Mr. Parloff says, “It’s so incredible” after Ms. Holmes tells him Theranos could essentially replicate everything a competitor’s lab was doing. She laughs and agrees.

Jurors have heard Theranos’s devices could never perform more than roughly a dozen types of blood tests, and the rest were done on commercial devices.

Mr. Parloff testified that Ms. Holmes didn’t tell him Theranos was using third-party commercial analyzers, even after he asked about it directly before publishing his June 2014 article.

In another audio clip, Mr. Parloff asks why Theranos was doing regular arm-vein draws on patients when the company’s technology touted using just a few drops from a finger prick.

The chief executive’s answer meanders, but mostly blames capacity constraints. “Our whole business is eliminating the need for people to do venipuncture unless they want to,” she tells him. “Everything we do is about eliminating that.”

Jurors have heard that patients who went to Walgreens-based Theranos testing centers had their blood drawn by a traditional needle-in-the-arm method about 40% of the time.

Write to Sara Randazzo at sara.randazzo@wsj.com and Heather Somerville at Heather.Somerville@wsj.com