But the trial was quickly suspended when a lawyer for the victim said she was suffering from “psychological problems” and was “not in a position to testify”, a court spokesman told AFP.
It was not immediately clear when the trial would resume.
The case, which shocked Spain, centres on an incident that allegedly took place between two contestants following an alcohol-fuelled party in November 2017 when the victim was unconscious.
Although the footage never aired, producers of the hit show came under fire for their handling of the incident after they confronted the victim, who was 24 at the time, with video evidence of an assault she had not been aware of.
“Big Brother” is a hugely popular reality show featuring contestants locked in a purpose-built house for weeks on end with their every move tracked on camera 24 hours a day.
Viewers then vote off the contestants one by one.
The trial focuses on testimony from the victim, who says she was raped by a fellow contestant while she was in a clear state of inebriation.
Prosecutors, who said the pair had been in a relationship for “about 50 days”, are pursuing the matter as a case of sexual assault.
According to a statement released by the prosecution, the woman got into bed fully dressed while the man took his clothes off and “began making clearly sexual movements under the duvet despite the fact… she was mumbling weakly ‘I can’t’.
The footage also shows her “raising her hand twice as if wanting to tell him to stop”, prosecutors said.
They said the defendant had covered them with the duvet, removed her clothes and “continued touching, rubbing and other clearly sexual movements… despite the fact she was already in a state of unconsciousness”.
After about 10 minutes, when she pushed the duvet aside, the production crew realised “she was unconscious” and moved to intervene, “not realising until that point what was going on because the defendant had covered them both with the duvet”.
The victim only became aware of the alleged assault when the producers showed her the footage the next morning, causing her to break down.
‘Never asked me’
The story only became public two years after the alleged assault, when El Confidencial news website published footage of producers showing her the clips.
In it, she can be seen in the so-called confession room, where contestants talk about their experiences, becoming increasingly upset as they show her the bedroom footage, tearfully pleading with the unseen producers to stop.
“They never asked me if I wanted to see that… if they asked, I would have said no,” she told El Confidencial.
She added that the producers should have brought in a therapist or someone to help her deal with the shock.
Dutch firm Endemol Shine Group, which owns the Spanish company that produces the show, said it “regrets” showing her the footage in the confession room.
Following the incident, the producers kicked the young man off the show, which is broadcast on Telecinco, Spain’s most-watched TV channel.
If convicted of sexual assault, he risks facing two-and-a-half years behind bars with prosecutors also asking for a 6,000-euro fine ($6,800).
They are also claiming the same amount in damages from the production company for showing the footage to the victim.