Earlier this week Spanish police arrested a half-dozen members of a human trafficking gang that lured four girls from Nigeria to Spain with the promise of jobs but instead forced them into prostitution and kept them there under threat of juju, or voodoo magic retribution.

“The Local,” an English-language Spanish news organization, reported that “Officers rescued four victims and arrested six members of the organization that used juju voodoo rituals to sexually exploit women… The traffickers had put the women through a juju voodoo ritual that used the victims’ fingernails or (hair) and involved animal sacrifice in front of idols in a temple in order to ‘guarantee that the women complied with everything they demanded, under threat of death to them and their families.’”

Voodoo Dolls Shed Light On Domestic Spats

The women had been taken from Nigeria overland to the Moroccan coast, where they then went by boat to Lanzarote, the easternmost of the Canary Islands. The operation was conducted as part of Spain’s “National Police Plan Against Trafficking in Human Beings for Sexual Exploitation,” launched in 2013.

The girls’ belief in -- and fear of -- powerful magic prevented them from going to authorities. In many countries throughout the world belief in witches is common, and black magic is considered part of everyday life. A 2010 poll of 18 countries in sub-Saharan Africa found that over half of the population believe in magic. Witch doctors are consulted not only for healing diseases but also for placing or removing curses, and many Africans fear that witch doctors -- or those who hire them -- have power over their lives and health.

VIDEO: How Superstitions Work

In her book “The AIDS Conspiracy: Science Fights Back,” Nicoli Nattrass, director of South Africa’s AIDS and Society Research Unit, notes that there “is a rich South African literature suggesting that many black people believe that HIV may have spiritual causes, notably witchcraft attacks.”

Those who subscribe to this belief system may sincerely fear that they could get AIDS simply by disobeying their pimps and traffickers or going to the police. Whether the traffickers believe in magic or curses is irrelevant; what’s important is that the victims do.

Spanish law enforcement authorities might take a cue from the British, whose government has dealt with this issue recently. Earlier this year the British government’s anti-slavery commissioner, Kevin Hyland, announced plans to prosecute sex traffickers by “reversing” the curses cast upon the victimized women.

Officials in Nigeria have located witch doctors believed to have placed curses on the victims and forced them to remove the curse or face criminal prosecution. This is an innovative -- and likely effective -- way of using psychology and folklore in service of justice.