Women shout slogans during a protest against sexual abuse in Pamplona, northern Spain. Photo / AP

Two years ago, an 18-year-old was allegedly gang-raped at the Running of the Bulls festival in Pamplona, Spain.

One night, the woman told police, five men in their mid-20s offered to walk her to her car. But instead of accompanying her to the vehicle, they pinned her against a wall, told her to "shut up," then took turns sexually assaulting her. One man stole her phone before they left, she alleged.

The woman was later found curled in a fetal position, crying in "a distraught state." She went to the police, who made arrests the next day.

The subsequent trial in what has been called the "Wolf Pack" case, named for a WhatsApp group of which the defendants were members, consumed Spain's attention for nearly two years.

Much of the trial revolved around short videos the defendants took of the woman during the attack. In the clips, the woman is seen in a "passive, submissive stance," with her eyes closed.

The men's lawyers said this was evidence that she'd consented. They also pointed to a report compiled by a private investigator who secretly followed the victim in the days after the incident. He took pictures of her smiling and laughing with friends - evidence, the defence team said, that the woman had not been traumatised.

The woman's lawyers pushed back against the idea that she had offered her "consent."

"The defendants want us to believe that on that night they met an 18-year-old girl, living a normal life, who, after 20 minutes of conversation with people she didn't know, agreed to group sex involving every type of penetration, sometimes simultaneously, without using a condom," prosecutor Elena Sarasate said, according to the Guardian.

The judge did not allow the jury to consider the WhatsApp chats among the men, who texted "us five are f---ing one girl" and "there is video" shortly after the attack. In other chats, the men joked about drugging women, then raping them. One even shared video of one of the men assaulting another woman, who appeared unconscious.

On Friday, the men were acquitted of sexual assault, a charge that includes rape. They were found guilty, instead, of the lesser charge of "sexual abuse" and sentenced to nine years in prison. (The woman's lawyers had sought 22 years.) Each man must also pay the woman about US$12,000.

That is not nearly enough for many in Spain.

In the wake of the verdict, tens of thousands of people have taken to the streets in protest. Holding signs declaring, "It's not sexual abuse, it's rape," activists rallied in Madrid, Barcelona, Valencia Pamplona and Alicante. An online petition calling for the disqualification of the trial's judges has gathered more than 1.2 million signatures.

Thousands demonstrate against Pamplona gang rape ruling in Spain - video

— The Guardian (@guardian) April 29, 2018

State prosecutors say that they will appeal the ruling.

Even Spain's national police force came out strongly for the woman, tweeting "No is no" a dozen times shortly after the verdict.

Politicians have promised to rethink Spain's laws on sexual violence. Right now, a victim must prove that a perpetrator was violent or intimidating to gain a rape conviction. Many women's rights activists say that sets the bar too high.

An editorial in El Pais noted that violence or intimidation can be hard for survivors to prove. It "leads to the painful question of just how much a person needs to fight to avoid being raped without risking getting killed, and still get recognised as a victim of a serious attack against sexual freedom while ensuring that the perpetrators do not enjoy impunity," the newspaper said.

"The Government has been, is and always will be with the victims," Íñigo Méndez de Vigo, a spokesman for the Government, told reporters.

Sexual assaults have plagued the Running of the Bulls festival. Women routinely report being groped, or worse. At the 2015 festival, a British woman was allegedly assaulted by a group of men in a bathroom.