This week, Theranos founder Elizabeth Holmes and her fiancé, Billy Evans, were spotted prancing around San Francisco’s Marina District with wide grins as they walked Holmes’ Siberian husky, Balto.

She had shed her infamous black turtleneck (inspired by her hero, Steve Jobs) for a white T-shirt and leggings. He sported a black tee that read, “Take a Walk on the Wild Side.” They looked every inch the ordinary, happy, engaged couple.

Anyone who saw them would never have guessed she is facing 20 years behind bars for wire fraud as part of an alleged scheme to defraud investors, doctors and patients. Or that she is considered one of the biggest scam artists of her generation and accused of putting lives in danger.

But despite her pending trial (her next court appearance is April 22), the 35-year-old Holmes and 27-year-old hotel heir are moving full steam ahead in planning a future together.

“The wedding invites were sent out about two weeks ago,” a former colleague of Evans’ said, adding that the couple got engaged three or four months ago.

“He gave her his MIT signet ring,” said the colleague, who worked with Evans at Luminar Technologies, a Palo Alto, Calif., firm that produces sensors for self-driving cars. “Billy and the MIT ring, they are inseparable. He always wore it on his pinky finger.

“He could snap his fingers and have a triple-A diamond engagement ring instantly if he wanted to. But if you give her some extravagant ring, it could end up owned by the feds if she has to give up her material possessions.”

In March 2018, the Securities and Exchange Commission accused Holmes of conducting “an elaborate, years-long fraud” and duping investors out of $700 million by falsely claiming to have revolutionized medical testing with a diagnostic device that could use a mere finger prick’s worth of blood. (She settled with a $500,000 fine and agreed not to serve as an officer or director of a public company for 10 years.)

‘His family is like, ‘What the f–k are you doing?’ It’s like he’s been brainwashed.’

She has become the subject of national obsession as her jaw-dropping maze of lies and deception has been chronicled in John Carreyrou’s book “Bad Blood,” as well as a recent HBO documentary, “The Inventor,” and the popular podcast “The Dropout.”

Holmes — whom Time magazine declared one of the world’s most influential people in 2015 — has gone from being one of Forbes’ Richest Self-Made Women, with a net worth of $4.5 billion, to having nothing.

People close to Evans, who graduated from MIT in 2015, are trying to make sense of the relationship. Sources told The Post that Evans’ image-conscious parents, William and Susan — who own three top hotels in Southern California, including The Lodge at Torrey Pines in La Jolla — are flabbergasted by their son’s decision to marry Holmes.

(Evans, his family and Holmes did not respond to requests for comment.)

“His family is like, ‘What the f–k are you doing?’ It’s like he’s been brainwashed. [He says,] ‘The media has it all wrong about her,’” said one San Francisco techie.

“He’s had a lot people very close to him sit him down and have a talk,” the colleague said, before cataloging the litany of warnings given to Evans.

“‘This could be the biggest mistake you’ll ever make.’ ‘The negativity around her could blow back on you.’ ‘You’ve never encountered anything like this.’ ‘You need to think hard about what you’re doing.’ ”

Still, the couple is undeterred.

“It’s kind of like Billy is her shiny new toy. She’s super enthusiastic about being with him,” the colleague said.

“The relationship is opportunistic for the both of them. Elizabeth needs a lot of support in her life right now, and Billy is looking for whatever way he can raise his profile.”

Even if that way is through a pariah.

A relationship with Holmes “will destroy your social value,” the colleague added. “But you will get something else in return” — namely, fame.

Before Holmes, the 6-foot-4 Evans was a playboy with a mission.

“I met two of his ex-girlfriends. They were both Instagram models, and he was super proud of that fact,” the colleague said. “He would date young, absolutely drop-dead-gorgeous girls [with big followings].”

The colleague added that Evans religiously tracked his social-media followers and likes. (Since news broke of his and Holmes’ relationship, Evans appears to have deactivated his Instagram and Facebook accounts.)

Evans met Holmes at a Bay Area party in the summer of 2017.

“Days later, I was hanging out with Billy and he said, ‘You won’t believe who I met! She’s not as the articles portray her to be,’” the colleague said.

As Evans and Holmes’ relationship heated up, Holmes would visit the Luminar offices with dog Balto “a lot,” the colleague recalled.

The drop-bys left many Luminar staffers uneasy, especially as the couple would often powwow with Luminar founder and CEO Austin Russell.

(A Luminar representative said Holmes “did not frequent the company’s office and had no business with Luminar Technologies Inc.”)

“It was inappropriate for her to be in the office. Luminar has been in a constant state of flux for a year and a half,” the colleague said, referring to recent layoffs there. “And then you have this total fraudster in the office while you have investor meetings.

“If I was an investor and I saw [Holmes] walking down the hallways, I’m going to be like, ‘Holy s–t, get me out of here!’”

Marriage to a potential felon wasn’t supposed to be Evans’ destiny. He and his two younger siblings grew up in the lap of luxury in San Diego.

“This is a pampered, wealthy family,” said a former employee at Francis Parker, the private school Evans attended.

His grandfather founded Evans Hotels in 1953, and it’s now run by Evans’ father and aunt.

“Descriptive words that come to mind are: San Diego old guard, generous to charities, never pretentious, and very powerfully connected — very,” said Margo Schwab, publisher of the San Diego Social Diary.

“The father has a fabulous old car collection that’s housed in a building,” added the former school employee.

Evans played volleyball in high school and at MIT, where he majored in math and economics.

“He always was very independent,” said an MIT friend of Evans’. “He doesn’t really care about what the rest of the pack or group or team thinks.”

After graduation, Evans tried to create a health-care startup that would charge wealthy Chinese people a large fee to be shuttled to the US for concierge medical attention — complete with “a chauffeur, beautiful hotels, the best health care,” said a source close to Evans.

“Then he realized that it’s actually very hard to get in with the affluent Chinese community if you’re not fluent in Chinese, so he dropped that.”

Instead, Evans worked at LinkedIn in San Francisco for two years before he was lured to Luminar by Russell. Evans had charmed Russell’s then-girlfriend on a flight, and she rallied for him to get hired. His title was manager of special projects, but his co-workers were never sure what his duties entailed.

“He was a bit of a showman. He was wandering around with absolute purpose, but no one knew what that purpose was,” said the colleague.

“He was Austin’s lieutenant, Austin’s secret police.”

Evans allegedly played bad cop for conflict-averse Russell.

“Austin hired Billy, this sort of good-looking guy who can strut around the office and tell people what to do. And if there’s blowback, he would say, ‘Listen, this is what Austin wants — and if you don’t do it there will be consequences,’ ” the colleague said.

(The Luminar representative said, “The speculation that he was a right-hand man to the CEO is inaccurate.”)

Evans’ closeness with Russell made his departure in January mysterious, though staffers speculate he was let go with severance because the publicity surrounding the relationship could have been a liability. (“Mr. Evans’ departure … was prior to any publicity of his reported personal relationship with Holmes that the company is aware of,” said the Luminar rep.)

According to the colleague, Evans stated a desire to start his own company post-Luminar. Recently, he traveled to South Africa (sans Holmes) for a potential business venture.

‘Some friends are saying, ‘I want to go to this wedding because I want to see this spectacle.’’

For now, it seems he and Holmes are content simply enjoying each other’s company — and that of their roommate, Evans’ best friend and former Luminar co-worker, Andrew Goldberg.

The three live in Holmes’ luxury rental apartment in San Francisco, where she moved after breaking up with Ramesh “Sunny” Balwani, 54, the former president and chief operating officer of Theranos who is also charged with wire fraud.

And despite the barrage of bad press engulfing Holmes, who has become one of the most villainized women in America, the couple is hardly hiding. They attended Burning Man last August, days before Theranos was dissolved. They are fixtures in the Fillmore District neighborhood, where they go to Loving Cup for frozen yogurt and drinks at The Snug.

While they’re cozying up over dessert, Evans’ friends are left with a bad taste in their mouths.

“We’re all shocked,” said an MIT volleyball source. “He seems like he had a solid head on his shoulders and had common sense and was a good judge of character … How does a rational, very intelligent person reach such a different conclusion about a person [than the rest of the country]? It doesn’t make sense.”

Some Silicon Valley techies are torn over whether to even attend the controversial couple’s nuptials.

“It was shocking [when the invitations went out],” said the colleague. “Some friends are saying, ‘I want to go to this wedding because I want to see this spectacle,’ and others are like, ‘I’m not going. I don’t respect her.’ ”

But the colleague disregards worries that Evans was “brainwashed” by Holmes, saying he’s too savvy to be manipulated, even by a mastermind.

“He’s the guy who pulls the wool over your eyes,” the colleague said. “It’s not the other way around. It’s never been the other way around.”