Meanwhile, legal experts called the focus on defendants' rights and due process good for the beleaguered justice system.
"I understand that right now we are in a difficult and confusing moment, but the message has been given: the procurement of justice has to follow due process," said Ricardo Sepulveda, a constitutional and human rights expert who heads the National Citizens Observatory for Security, Justice and Legality. "There is no other path for us to get out of the security crisis that we have in this country."
Few, however, seemed to believe that Cassez's release will lead to any meaningful change in a system where an estimated 98 percent of crimes go unprosecuted. Innocent people frequently are jailed in Mexico while criminals behind the country's astronomically high kidnapping rate are seen to enjoy widespread impunity.
Isabel Navarrete, a 33-year-old mother feeding frozen yogurt to her baby on Mexico City's broad Paseo de la Reforma boulevard, blamed the country's institutions.
"There is no credibility in the institutions of justice and lot of pain and indignation among the families who suffered," said Navarrete, calling the national handwringing over the case a "smoke screen."
"If anything, it will get a little worse," she said.
Roberto Hernandez, director of the film Presumed Guilty, a documentary about a Mexican man falsely imprisoned for murder, said both the experts and the people are right. "The public has every reason to feel betrayed," he said. "The process the Supreme Court followed and the judicial process in general is so poor, it's designed to create mistrust."
In France, Cassez was greeted by a red carpet and television cameras upon her return. The 38-year-old looked rested and buoyant after seven years in a Mexico City prison. "I was cleared," she declared to the throngs of journalists waiting to receive her, though the justices pointedly did not rule whether she was guilty or not.
The Frenchwoman has said she lived with her then-Mexican boyfriend, Israel Vallarta, at the ranch where the kidnapping victims were held, but didn't know they were there. At least one victim identified Cassez as one of the kidnappers, though only by hearing her voice, not by seeing her.
She told BFM television on Friday that she may have been naive to get involved with Vallarta, who is still awaiting trial, but added: "Who at 30 hasn't had a relationship like that?"