Editor's Note: (Yasmeen Hassan is the global executive director of advocacy group Equality Now. She previously worked on the implementation of the Convention on the Elimination of all Forms of Discrimination Against Women (CEDAW) and the United Nations secretary general's study on violence against women. Follow her on Twitter. The opinions expressed in this commentary are solely those of the author.)
(CNN) The horrific gang rape of a 16-year-old girl in a slum in Rio de Janeiro, Brazil, by at least 30 people has once again brought the issue of sexual violence into the international spotlight. Images of the drugged, naked and unconscious girl were subsequently posted on social media, fueling national outrage. But the survivor has spoken about her doubts that she will be able to obtain justice.
"If I have to wait for the justice system, they've already shown that nothing is going to happen," she told CNN affiliate TV Record in the presence of her attorney.
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The government news agency Agencia Brasil reported that only two arrests have been made and four alleged perpetrators are being sought.
According to the Washington Post, the victim also claimed that the police officer leading the investigation asked the victim if she was in the habit of having group sex. He has since been replaced by a woman.
And more recently, the six-month sentence handed to Brock Turner, a former Stanford University swimmer, for sexually assaulting an unconscious woman has sparked an outcry.
Sexual violence is largely a hidden epidemic. For every reported crime, the Sexual Violence Research Initiative suggests that in some countries including Brazil only five percent of adult victims of sexual violence report to the police.
According to the World Health Organization, 14.8% of women over 17 in the United States have been raped and that national data on rape and sexual assault in the United States shows that about 1 out of 10 sexual assaults involve multiple perpetrators.
While data on rape is spotty at best, the 2013 "Dossiê Mulher" (Women's Dossier) shows that between 2012 and 2014, the number of reported rapes in Rio de Janeiro has fallen by 2-3% annually. However, based on these figures, this still meant that almost 400 women and girls on average in Rio were raped every single month.
Governments around the world have made repeated commitments to ending violence against girls and women, but there has been little political will to follow through with meaningful change.
And this issue is not confined to developing nations. Approximately 19,000 men and women suffer sexual assault each year in the U.S. military, former Defense Secretary Leon Panetta has said in 2012, although he noted that only 3,200 of these were reported. In the U.K., around 85,000 women are raped each year, Rape Crisis England and Wales estimated in 2013.
Impunity for crimes of sexual violence is rampant. This can start with the "shame" associated with sexual violence that deters victims from reporting crimes in the first place, to legal systems re-victimizing victims through disbelieving, insensitive police, prosecutors and judges; to legal procedures that are cumbersome and demeaning and lengthy legal proceedings that are aimed at protecting the right of defendants to prove their innocence -- often at a huge cost to victims.
In over a dozen countries so far, through Equality Now's 'Justice For Girls' program, we have taken on cases of sexual violence against girls in order to highlight the gaps in legal systems, which prevent access to justice and create impunity for such crimes, and to set important legal precedents. Through these cases, we have seen how hard it is for girls to get justice and therefore how easy it is that rapes continue with impunity.
In a recent gang rape case in Kenya, 16-year-old "Liz" was thrown in a ditch and left to die. Initially, her rapists were sentenced to mow grass as punishment, but following local and international efforts, the sentence was increased to 15 years for gang rape and seven years for causing grievous harm.
In Ethiopia, 13-year-old Woineshet's rapist and abductor was set free as the judge did not believe that she had been a "fresh virgin". It took 15 years for her to finally get the justice she deserved from the African Commission, which held Ethiopia liable for failing to provide her adequate legal protection and awarded her damages.
These cases all illustrate relatively common failings in legal systems to protect women and girls as well as patriarchal mindsets. Gaps exist in some rape laws, which exempt rapists from punishment if they marry their victim. Others allow rape to legally take place within marriage. Countries have only recently considered this to be an urgent issue. The United Kingdom criminalized marital rape in 1991, while North Carolina was the last American state to ban it as recently as 1993.
It is also evident that the attitudes of police, prosecutors and judges can have seriously adverse impact on rape victims.
A 2013 research paper on women's access to justice in Pakistan showed that very often the judicial focus was not on the actions of the rapist, but on the behavior and even sexual history of the victim -- not to mention the gruelling and demeaning cross-examination of victims at the hands of defence lawyers.
I have also witnessed girls who are victims of rape and child pornography in the U.S. decide not to file charges, as they anticipate such violations by defence lawyers.
To make lasting change, governments must have the political will to enact and enforce strong laws to protect women from sexual violence. They must hold accountable those government officials who fail to implement the law or traumatize victims. They should review legal procedures to ensure that victims of sexual violence are not re-victimized and ensure adequate punishment for perpetrators, so that others are deterred.
There is no easy fix to changing attitudes around the world, but effective victim-centered legal systems are a good place to start. This means that victims must have access to justice from the inception of a case, with trained and sensitive investigators to completion. They should also have sufficient restitution and services to help them on their path to recovery.
Brazil is now in a position to respond to the growing outrage and make this promise a reality, but only time will tell how it chooses to proceed.