(CNN) -- Mexico's Supreme Court on Wednesday ordered the release of a Frenchwoman who had been sentenced to 60 years in prison for her alleged role in a kidnapping ring.
The high-profile case of Florence Cassez has drawn national attention in Mexico and increased diplomatic tensions with France.
Cassez was convicted on kidnapping charges in 2008 and sentenced to 60 years in prison, but Wednesday's 3-2 Supreme Court decision overturned that ruling and ordered her release.
She was expected to depart Mexico for France Wednesday night, CNN affiliates reported.
One justice had proposed that a lower court reconsider its sentence against Cassez, calling witness testimony identifying Cassez as a kidnapper invalid. But ultimately, the court ruled that there were so many significant irregularities during Cassez's detention and trial that she should be released from prison immediately.
"These violations of the human rights of Florence Cassez are so serious that they create a corrupting effect in the entire process that makes it impossible for the Supreme Court to validate this process, this detention, all of these violations," said Arturo Zaldivar, one of the justices.
Mexican authorities arrested Cassez and her boyfriend in 2005. They accused her of being part of the Zodiaco criminal gang and participating in at least three kidnappings.
Cassez has argued that she did not know about her boyfriend's activities in the gang, disputed the testimony of witnesses who identified her and emphasized that Mexican police staged her arrest for television cameras.
On Wednesday, Cassez's lawyer said his client was "very excited" about the ruling.
"It is a historic decision and a precedent in the defense of human rights," attorney Agustin Acosta said.
But a well-known anti-crime advocate in Mexico criticized the high court's decision.
"It seems to me that this opens the door to impunity and leaves the victims empty-handed," said Isabel Miranda de Wallace, president of a prominent Mexican anti-kidnapping group.
For years, French officials have pushed for Cassez's release and asked Mexico's Supreme Court to consider the case.
French President Francois Hollande praised the court ruling.
"The thoughts of the head of state go to Florence Cassez, her family and those close to her," Hollande's office said in a statement. "For them, as for all of those who have mobilized for our compatriot, this is a particularly painful period that has come to an end."
French Prime Minister Jean-Marc Ayrault released a statement expressing his "deep solidarity" with Cassez "and everyone who helped her in her fight for truth and justice."
"He welcomes the prospect of seeing Florence Cassez return to France as soon as possible," the statement said.
CNN's Alex Felton, Rene Hernandez, Rafael Romo, Rey Rodriguez and CNNMexico's Tania L. Montalvo contributed to this report.