Judge Arturo Zaldivar wrote that Cassez had been denied immediate access to consular rights, had not been immediately presented to a prosecutor on her 2005 arrest and had not been presumed innocent, a statement said Wednesday.
The violations left the Frenchwoman, who is now aged 37, “totally without defence,” it said.
Cassez’s lawyer, Agustin Acosta, said the ruling should be made on March 21.
The proposal slams an alleged reconstruction of Cassez’s arrest set up by the authorities for TV cameras one day after she was actually detained in late 2005, and says officials were “consciously deforming reality.”
Mexican appeal judges last year rejected the argument that Cassez’s conviction was tainted, despite the staged arrest.
Federal police accused Cassez of being involved with a gang of kidnappers known as the Zodiacs, allegedly run by her ex-boyfriend Israel Vallarta, with whom she was arrested.
Cassez has denied any knowledge of the crimes, and claims she was made an example of by authorities keen to show a firm stance against rampant kidnappings.
The case has strained diplomatic relations between Mexico and France. Mexico’s government canceled a year of Mexican cultural celebrations in
France after French President Nicolas Sarkozy said he would dedicate them to Cassez.
Sarkozy tried unsuccessfully to persuade Mexico to transfer Cassez to a French prison.
Five Mexican rights groups welcomed Wednesday’s proposal in a joint statement saying they supported the move.