Octavien Ngenzi, 60, and Tito Barahira, who will be 67 in June, were convicted in 2016 for crimes against humanity and genocide over the “massive and systematic summary executions” of minority Tutsis by ethnic Hutus in Kabarondo in 1994.
Their case is one of about two dozen still underway in France, which opened trials and issued arrest warrants over the killings of roughly 800,000 people because some of the victims were French citizens.
Arrested in France, Ngenzi has already spent eight years behind bars, while Barahira, who is receiving dialysis treatment, has been held five years.
Their sentence was the toughest handed down in France after that of Pascal Simbikangwa, a former Rwandan intelligence agent who received 25 years in a landmark 2014 conviction upheld in 2016.
The two men have maintained their innocence in the massacres at Kabarondo.
More than 2,000 people were killed on a single day as they sought refuge in a village church, according to its pastor.
Ngenzi’s lawyers say they intend to call Rwanda’s current defence minister, James Kabarebe, to the stand over his role in the Rwandan Patriotic Front, a Tutsi-backed force which eventually managed to halt the killings.
During the first trial, prosecutors accused Ngenzi of being an “opportunist” who “went over to the dark side” when the killings began, while Barahira was accused of denying that the genocide even happened.
“We expect the verdict to be upheld,” said Alain Gauthier, a campaigner for victims’ families, whose wife lost several relatives in the genocide.
The trial, which will include testimony from witnesses in the courtroom or via videoconference from Rwanda, will be filmed for posterity. It is set to close on July 6.