SAN JOSE — White-faced and speaking in a barely audible but firm voice, the wife of Silicon Valley real estate mogul Clyde Berg briefly took the stand Tuesday, presenting her version of events for the first time since he was charged with a horrific crime against her — outfitting her while she was nine months pregnant with a spiked dog collar and leash, chaining her at gunpoint to a bed for two days and sexually assaulting her with a golf putter.

But while Ellena Berg, 37, readily answered the first of many softball questions from prosecutor Alison Filo about how she and her now-74-year-old husband met (while the Swedish native was working for a local family as an au pair) and about why they married (so she could stay in the United States), she shocked the court by flatly refusing to answer two key questions during her 90 minutes of testimony. She is set to take the stand again Wednesday morning.

The questions had to do with what happened the night in 2010 when she was arrested on suspicion of domestic violence against her husband and what happened to end her two previous pregnancies.

“I refuse to answer that,” she said in response to one of the questions, prompting Judge Ron M. Del Pozzo’s eyes to widen.

It was too early to tell what ultimate effect Ellena Berg’s reticence will have on the judge and on the prosecution. But her refusal, while not unheard of, is highly unusual.

If she also declines to answer multiple questions at trial, the defense could seek to have her entire testimony struck on the grounds that Berg was denied his constitutional right to confront his accuser.

But Del Pozzo first must decide after the two-day preliminary hearing whether there is enough evidence to hold Clyde Berg over for trial. Unlike in a trial, the standard of proof is low. If the judge dismissed the charges, prosecutors would have the option of recharging him if new evidence turned up.

Berg is charged with two felony counts — corporal punishment of a spouse and penetration by a foreign object while the victim is tied and bound, which collectively carry a sentence of more than 15 years to life.

Prosecutors also must decide whether Ellena Berg is a credible witness. She has claimed in a 43-page civil suit that the bizarre incident last fall at their home overlooking the San Jose Country Club capped off 10 years of physical and sexual abuse.

But Berg vehemently denies the charges, contending he is the victim of a greedy scam aimed at getting around a restrictive prenuptial agreement. His denials might seem predictable, but he has mustered some supporting evidence, including gynecological reports that arguably show Ellena Berg did not sustain the degree of sexual abuse she asserts.

He is free on $3 million bail, released after a judge expressed some skepticism about how Ellena Berg managed to call 911 with her hands cuffed behind her back. Bloodied and bruised, she was found in September, tied up in a bedroom of their spacious home overlooking the San Jose Country Club.

Clyde Berg is the brother and business partner of billionaire Carl Berg, one of the richest people in the United States. The brothers developed campuses for many of the valley’s signature companies and recently sold their firm for $1.3 billion.

Contact Tracey Kaplan at 408-278-3482. Follow her at Twitter at @tkaplanreport.