A nurse who used Voodoo rituals to intimidate her victims has been convicted in England of trafficking five African women to work as prostitutes in Germany, reports Associated Press.

Jurors at Birmingham Crown Court convicted Josephine Iyamu on Thursday of being the ringleader of a network that brought the women from Nigeria to Europe.

Prosecutors say that in exchange for travel, the Liberian-born Iyamu charged the victims between 30,000 euros and 38,000 euros ($44,000) and made them work as prostitutes to repay the debt.

Though she claims to have been born in Liberia, Iyamu is believed to be a Nigerian from Edo State.

The victims also were forced to take oaths at a Voodoo or “juju” ceremony in which they promised to repay the debts and not to go to police.

Prosecutors say the rituals gave Iyamu psychological control over the women, who were too afraid to challenge her.