"It's obvious that this process made mistakes," Garmendia acknowledged. "Above all, this ruling is a message that the trafficking business will continue as usual."
Simultaneous demonstrations were held in Buenos Aires on Wednesday night to protest the verdicts.
One led by governing party politicians outside the main federal justice building was peaceful. Another, involving hooded youths outside the Tucuman provincial government's tourism promotion office, quickly got out of hand with protesters smashing windows, throwing rocks and setting fire to two garbage bins they tried to push inside the building.
Reinforcements arrived and riot police pushed back the protesters, regaining control of the situation.
Trimarco called on her supporters to keep the peace, even as she expressed her anger at a news conference Wednesday, accusing the judges of taking bribes.
The lead trial judge, Alberto Piedrabuena, didn't respond to the bribery allegations, but he countered in a local radio interview that the evidence failed to resolve reasonable doubts or overcome the principle of being innocent until proven guilty.
Prostitution remains legal in Argentina, but managing brothels and trafficking in people have been federal crimes since 2008, under a law Congress passed after lobbying by Trimarco.
Garre credited her ministry's enforcement of this law with saving 938 people last year from trafficking — 215 people from the sex trade and 723 from other workplace exploitation. She said more than 800 have been rescued so far this year.
Hundreds of women also have been saved by a foundation Trimarco created in her daughter's name in 2008 with seed money from the U.S. State Department's "Women of Courage" award. The foundation also provides legal help, but its lawyers have found that proving sex slavery is difficult without full support from the same police who often get paid to protect prostitution rings.
To date, the foundation has helped 20 former sex-trafficking victims bring cases against their captors, but they have yet to win a single case. Of these, 12 resulted in federal charges, but a handful were bounced back to even more uncertain justice in provincial courts around Argentina.
"They don't investigate. There's a lack of commitment and capability," said Agustin Araoz Teran, one of the foundation's lawyers, who called the Tuesday night's verdicts "an act of cowardice."
Teran joined Trimarco's movement after his father, a juvenile court judge in Tucuman, was shot to death in his home in 2004 after investigating local police officers who were allegedly freeing juvenile delinquents so that they could peddle drugs on their (the police's) behalf.