REIMS, France They are often compared to Serge and Beate Klarsfeld, the activist couple who came to fame in 1960s tracking down Nazis from France. But Alain and Dafroza Gauthier have their sights on Rwanda's 1994 genocide.
The pair have spent a decade searching for dozens of suspected accomplices of the massacre in the east African country who have since been living quietly in France.
France has now agreed to stage the first trial of a 53-year-old former soldier accused of arming and guiding the killers.
It is a victory for the Gauthiers and could help relations between the two countries as they try to strengthen economic and diplomatic ties although it could complicate them if the outcome does not please those Rwandans looking for justice.
"It's a huge satisfaction," Dafroza, a 59-year-old ethnic Tutsi from the southern city of Butare whose mother was killed in the genocide directed by Hutu extremists, said of the landmark trial slated for next February.
"But France really needs to speed up, because the witnesses are disappearing, and so are the killers."
Dafroza Gauthier has deep personal reasons for wanting justice. But her quest is wrapped up in the wider rapprochement between Rwanda and France since the genocide whose perpetrators President Paul Kagame once accused Paris of backing.
Its own economy struggling with sluggish growth, President Francois Hollande's government now sees east Africa's frontier markets as investment hotspots often more lucrative than those of its ex-colonies in the west.
France views Rwanda as essential to maintaining stability in Africa's Great Lakes, a vast zone including Uganda, Burundi, parts of Kenya, Tanzania and the Democratic Republic of Congo.
Rwanda too is keen to unlock largely dormant commercial ties: exports from France to Rwanda stood at a mere 16.1 million euros ($21 million) last year, while France imported goods from Rwanda worth just 3.6 million euros.
But the process is fragile. Rwanda is pleased that France is finally bringing suspects to trial but there is a risk the rapprochement could be set back if the trial results in a short sentence or acquittal.
"The Rwandans would not be happy at all with that," acknowledged one French diplomatic source.
Dafroza and Alain met in the early 1970s in Rwanda, where he went to teach French under a foreign aid program. A few years later, they met again by chance in France after she fled Rwanda to escape violence against Tutsis that was already simmering.
They got married and were raising a family in the northeast city of Reims, the center of France's champagne industry, when full-scale genocide erupted in Rwanda.
Over 800,000 ethnic Tutsis and moderate Hutus were slaughtered during a three-month killing spree by Hutu extremists that followed the fatal downing of a plane carrying President Juvenal Habyarimana.
As the bodies stacked up, the Gauthiers realized they could not sit in their comfortable French home and do nothing.
"Her life is my life. Her family is my family. It's also my family that has been assassinated," said Alain, 64, sitting next to Dafroza in the small home office where they work on cases.
"We very quickly found ourselves looking into who was behind the massacres. This is a battle that has been imposed upon us and we'll lead it as long as we have the strength to."
PILLARS OF SOCIETY
The couple started taking notebooks on visits to Rwanda, talking to survivors and collecting testimonies. It gradually dawned on them that many alleged accomplices of the killings were living lives of outward respectability in French cities such as Toulouse, Bordeaux, Lyon and the suburbs of Paris.
One high-profile suspect is Habyarimana's widow Agathe, whose extradition to Rwanda was refused by France but who lives in illegal limbo just outside Paris because her request for a residence permit was rejected.
Alain Gauthier said others come across as pillars of society, be it as practicing priests and doctors. "They try to be forgotten," he said.
To date they have filed, or have been involved with filing, some 20 legal complaints against alleged perpetrators. It has taken more than four years of judicial investigation for the first case to come to court -- 20 years after the massacres.
"It's very significant because the genocide suspects will no longer find the safe haven in France that they have today," Jacques Kabale, Rwanda's ambassador to France, told Reuters.
Before the genocide, France had been the main Western backer of Rwanda. But in its aftermath, relations between the two countries collapsed.
Kagame, a rebel leader whose government came to power after the genocide, accused France of training and arming the Hutu militias who were the main force behind the slaughter - an accusation Paris has always denied.
Diplomatic ties between Rwanda and France were broken off in 2006 when a French judge said Kagame and others had orchestrated the assassination of Habyarimana to trigger the bloodshed - an accusation he denies and which French justice has since dropped.
The first complaint in France against a suspected accomplice was filed back in 1995 and a legal change in 1996 made it possible for Rwandans suspected of being involved in the genocide to be tried in a French court.
Yet little happened and in June 2004, the European Court of Human Rights even fined France for its tardiness over one case.
Human rights associations denounced the slowness of the French justice system in convicting suspects, noting several Rwandans have already been tried in Belgium, Finland and Sweden.
"Without trying to put the blame on anybody, I think maybe France, or its justice system, was apprehensive and was not yet ready to deal with public trials," ambassador Kabale said.
Ties were restored in 2009 and a year later France officially recognized it had made "errors" in the country. Kagame made his first visit to Paris in 2011, stressing he wanted to move on and explicitly hailing new efforts in France to seek prosecutions.
Foreign Ministry spokesman Philippe Lalliot says France now sees Rwanda as an important partner with which it wants to develop ties further. The next 12 months will test how far and how fast that process can advance.
France in 2012 created a special genocides investigation unit and for Kabale, the February trial offers "a first glimmer of hope".
Ex-soldier Pascal Simbikangwa is charged with complicity in genocide and complicity in crimes against humanity. He risks a life sentence in prison with up to 22 years of mandatory jail.
"His trial will enable us to zoom in and get a close-up look at the genocidal regime," Dafroza Gauthier said of Simbikangwa, who was arrested in 2008 on the Indian Ocean archipelago of Mayotte, an overseas French department.
Simbikangwa, paraplegic since 1986 after an accident, acknowledges he was close to Habyarimana but denies any wrongdoing. "A myth has been constructed around him," his lawyer, Alexandra Bourgeot, told Reuters.
The trial comes as Rwanda marks the 20th anniversary of the genocide and activists hope it will create better understanding in France of the slaughter. They also hope Paris will mark the anniversary by sending a high-ranking official to Kigali.
"France must be there in a positive and constructive way," the diplomatic source said, stressing that no decision had been taken yet on whom France would send.
The Gauthiers hope the Simbikangwa trial will be just the first of a string of others, and say two other investigations are close to wrapping up.
Aside from the diplomatic significance of bringing the perpetrators to justice, for the Gauthiers it represents closure on a very personal level.
"I know I will be present, maybe not the entire time, but I will be there," Dafroza said. "During a trial, we talk about victims, about their lives. It is therapeutic." ($1 = 0.7600 euros)