Patrick Desbois has developed a keen eye for Ukrainian pensioners. The French priest -- a diminutive man dressed in black -- is standing on a village street and looking at two women walking by. They are the right age. "Go over there, quickly, and ask them," Desbois says to his colleague Andrej Umansky, a law student from Cologne. Both men have just arrived in Yaktorov by minibus.

"Did you live here during the war?" Umansky asks the women. That's always the first question.

One of the women nods.

"Did you see how the Jews were shot?" asks Umansky. When someone has answered the first question with "yes," this is always the second one.

The woman nods again.

She is another contemporary witness of the Holocaust in Ukraine who Desbois and Umansky have found. This has taken them one step further in their work: documenting the mass murder of Jews in this region.

For the past six years, the priest, the student and the others in their small team have been traveling through Ukraine and looking for old people, men and women over the age of 70.

An estimated 1.5 million Jews were murdered by German occupying forces in the area that constitutes today's Ukraine. Some of these people were deported to extermination camps in what is today Poland. However, most of the victims were shot by the occupiers in mass executions throughout the country.

Retracing the Steps of the Perpetrators

One of the largest massacres was in the Babi Yar ravine near Kiev. On two days in September 1941, more than 33,000 Jews were shot dead. This massacre has been investigated; there are books and films about it, and there is also a memorial there. Before the priest and his team arrived, not much was known about the many other killings. There were hardly any memorials; hundreds of thousands of dead had been forgotten.

The researchers retrace the steps of the perpetrators. Traveling from village to village, they conduct interviews with eye witnesses, find locals who will show them the sites of atrocities, search fields for spent cartridges, shoot films, take pictures and note down everything. They are usually on the road for a number of weeks in a row, traveling in teams of 10.

Over the past six years, they have questioned over 800 people in 330 towns and villages, and discovered hundreds of mass graves. This autumn their organization, Yahad-In Unum, will open a documentation center in Paris in collaboration with the Sorbonne University. The German Foreign Ministry has just made €500,000 ($717,000) available to allow them to continue their search.

The old woman in Yaktorov is prepared to answer additional questions. Her name is Anna; she is 82 years old. In the afternoon she is sitting at her living room table -- a tiny woman wearing a headscarf and a knit jacket, despite the heat.

Over the years, Father Desbois has developed a system that they now use to conduct all interviews. They inquire about a large number of details to refresh the witnesses' memories. What was the weather like on that day?

The weather was beautiful, says Anna, a sunny day.

It is important to ask the questions calmly. No interrogative tones, no judgments, no emotions.

"I was walking with my cows on the meadow in front of the village," says Anna. She was a young girl back then, 16, the daughter of simple farmers. Her answers are brief, and she glances mutely at the priest after each response.

It Was Much Worse for the Others

She had heard shots in the forest behind the meadow, and when it was quiet again, she went to have a look. She saw three pits with corpses lying in them. The pits were nearly filled with dead people, says Anna. She only remembers male corpses, and she can't say whether they were naked or clothed. A boy from the village was also there and they both stared into the pits. She only glanced for a moment, and then she ran away.

Patrick Desbois became a Holocaust researcher because of his grandfather, who was a prisoner of war held by the Germans in a camp in Galicia, in a small town called Rava-Ruska. When he later told his grandson about his internment in the camp, he said: It was much worse for the others. The old man never said who the others were, and his grandson didn't dare ask. When he later found a book with photos of Jews in a concentration camp, he realized what his grandfather had been talking about.

Desbois lived in Africa and India before joining the Catholic priesthood and becoming the secretary to the French Conference of Bishops for Relations with Judaism. He started to study the Holocaust, and visited Yad Vashem and Auschwitz. Nine years ago, he visited Ukraine for the first time and saw the town where his grandfather had been held.

During a second visit to Rava-Ruska, he asked about the other places. Thousands of Jews had been murdered in the town. But where? No one could tell him. Desbois refused to believe it at first, and then he simply could not accept it. He decided to look for the graves of the dead himself -- in a country that he hardly knew, and whose language he didn't speak. It would take two, perhaps three trips, he thought. He was furious, determined and far too optimistic.

Many eyewitnesses were children, younger than Anna, when the Jews were murdered in their towns and villages. The youngsters were curious and went to where the people had been shot. Others were enlisted by the Nazis to do manual labor. They had to fill in the pits or collect the clothing of the victims. These children were often plagued by guilt later on. Now many are recounting what they experienced for the first time.

Bones Lie Beneath the Meadows

Most of the mass graves are in western Ukraine, in the Galicia region. Galicia is also home to the village of Yaktorov, near the city of Lviv, where the Germans administered the region after they invaded the Soviet Union in 1941. The occupiers confined the Jews to a labor camp near Yaktorov. In the summer of 1943 the camp was closed and all prisoners were shot.

On the spot where the camp was located, Father Desbois is standing next to another witness and waiting for the old man to return to the present.

The priest rubs his eyes; he is exhausted. Desbois is 54 years old and constantly traveling to conduct research, attend conferences, or present the book that he has written about the project.

The old man yells disjointed words in German -- "Schweine, weg, weg" (or "get out of here you pigs") -- and holds an imaginary rifle in the air. Then he throws himself down in the grass, seemingly oblivious to the fact that he is wearing a light-colored, carefully ironed shirt. Flowers are blooming on the meadow, yellow and purple, and under the meadow lie the bones of the dead.

'Where Did the Marksmen Stand?'

A memorial stone to the murdered Jews has stood for a number of years on one edge of the former camp compound. That is inconclusive proof, as far as Desbois is concerned. The stones often stand at the wrong location.

The old man jumps up and straightens his white hair. The witnesses often slip back into the past when they return to the sites of the atrocities, says Desbois.

The man's name is Bogdan and he was eight years old when he observed a number of shootings from a distance. When they brought the Jews to the pits, a German played on his harmonica, and afterwards the earth was drenched in blood, he says.

"Where did the marksmen stand?" the priest asks him.

The old man points to the right-hand side, where the meadow gently slopes upward. It is not the side with the memorial stone.

Andrej Umansky, the student from Cologne, runs to get the team's ballistics expert -- a large, taciturn Ukrainian with a crew cut who everyone calls Misha -- and walks with him up the small hill. Misha moves a metal detector back and forth over the ground. After 30 seconds, they make their first discovery, a cartridge case. "German" Misha yells. It is possible to recognize the ammunition based on stamped numbers and letters. They find a second and a third German-made cartridge. The killers have not eliminated their traces. Then the metal detector emits another sound, indicating a lighter metal. This leads them to a clump of earth, and Umansky and Misha begin to scrape around it. In the soil they find a Star of David made of silver. It is a pendant as large as a one-euro coin.

Umansky fetches plastic bags from the bus to pack up the cartridges and pendant. Later on, he will take notes on the location of the evidence.

Andrej Umansky was born in Ukraine and came to Germany as a child with his family. He was spending a voluntary year performing social services in France when he heard that a priest was looking for interpreters for a trip to Ukraine. Umansky volunteered. His father comes from a Jewish family in Kiev that was evacuated to the non-occupied zone of the Soviet Union before the massacres.

'We Could Stop Anywhere and Find a Mass Grave'

Umansky, 26, still has a somewhat boyish appearance. He always first flips to the sports section in the newspaper. But when he talks about his work, he sounds like a veteran historian. Following his first trip, he began to research the occupation in German archives. Meanwhile his travels to Ukraine have been eclipsed in number by his trips to Ludwigsburg, Germany -- to the Central Office for the Investigation of National Socialist Crimes, where he pours over the postwar investigation reports. At student parties back in Cologne he tries to avoid the issue.

Evening has fallen and the men are sitting in the bus back to Lviv. Umansky opens his backpack and pulls out his laptop where he has saved databases, records, historical maps and satellite images of Galicia.

Father Desbois gazes out the window at the flat, expansive land in the twilight, and the horse carts that the minibus passes. "It's beautiful here, isn't it?" he says. "We could stop anywhere here and find a mass grave."

Umansky looks up from his laptop and says: "Durchgangsstrasse IV." That's what the occupying Germans called the road that they are driving on. It extends from Krakow south into Ukraine. It was along this road that the Germans established camps for the Jewish forced laborers. They drove along this road to the villages to shoot the Jews. "We are taking the same trips as the perpetrators," says Desbois.