In the Holocaust, the majority of victims were annihilated through a process of industrialized mass murder, making it often difficult to ascribe personal responsibility to an individual murderer. Given the fact that most of the victims were identified, robbed of their possessions, concentrated and deported from their homes to distant death camps - where they were annihilated by a complex system especially established to facilitate their exploitation and extermination - responsibility for the murders is diffuse and shared by many participants. Even in the cases of those shot dead by the Einsatzgruppen mobile killing units and their local helpers in Eastern Europe, it is usually impossible to determine who murdered specific victims. The incredible difficulty of determining direct accountability for the murder of individuals helps explain the paucity of efforts by survivors and the members of their families to track down the killers who murdered their loved ones during the Shoah. In fact, such cases have been extremely rare (the ultimately successful efforts of German journalist Peter Finkelgruen to bring his grandfather's murderer Anton Mallot to justice being a notable exception). As time goes by and the difficulties mount, such efforts become even less likely to succeed. UNDER THESE circumstances, the story of how Israeli businessman Ronny (Aharon) Lerner was able this past summer to track down one of the persons who murdered his grandmother and five of her children, as well as two other young Jews, is truly remarkable. Lerner was able to confirm that, on the night of October 30, 1943, five Poles - Jan Sadowski, Waclaw Stelmoszuk, Franciszek Uzdowski, Jozef Radczuk and Deniek Bozyk - murdered his 45-year-old grandmother Gitel Lerner and her daughters Miriam, 22, and Chana, 20; and her sons David, 17, Zvi-Herschel, 15, and Chaim, 13, as well as two young Jews named Zefryn and Pomerantz on the farm of Uzdowski in the village of Przegaliny near the town of Komarowka in the vicinity of the city of Lublin. Before killing the Lerners, the murderers tortured them and raped the two daughters. As the background to these murders, it is important to understand the plight of Polish Jews attempting to hide in those days. The Lerner family, who had been living in Komarowka, where they owned a bakery before the Shoah, had been approached in the summer of 1942 by Jan Sadowski, who offered to build them a hideaway in the nearby village at their expense, in return for the cost of the hiding place and a hefty monthly sum for rent and maintenance. Given the rapidly deteriorating situation in Poland, the Lerners agreed, and in April 1943, after the rest of the family had been incarcerated in the Miedzyrzecu Ghetto and Chana and three of her brothers had escaped from a deportation train to Majdanek, the mother, Miriam and the four escapees moved to the hideaway prepared by Sadowski along with Zefryn and Pomerantz, who had been in the same ghetto. The Lerners kept their part of the bargain, but the opportunity to rob them of their valuables apparently motivated Sadowski and his accomplices to murder them six months later. Despite near-heroic efforts by Ronny Lerner's father, Yoseph, who survived as a non-Jew in Warsaw, verified the identities of the killers and collected incriminating testimony shortly after the end of the war to bring them to justice, only one of the murderers was prosecuted and punished. THUS, SEVERAL months ago, posing as an American researcher, Lerner came face to face with Radczuk, the only perpetrator still alive, who actually admitted his role on film. Lerner submitted the evidence in his possession to the Polish Institute of National Memory (IPN), which is responsible, among many things, for the prosecution of World War II crimes, and an official investigation has been initiated. But the task of prosecuting local murderers of Jews is not an easy one in contemporary Poland. Although the IPN has opened hundreds of investigations of Holocaust crimes, only one local Nazi collaborator has been convicted and punished since the establishment of the Polish prosecution agency. And in fact, of the two extraditions pursued by the IPN in recent years one was of Bogdan Koziy, a Ukrainian policeman who murdered Jews in Eastern Galicia; but the other was of a Jew living in Israel named Salomon Morel, who ran a detention center for suspected Nazis and others after the war and is accused of "genocide." This reluctance to face the complicity of numerous individual Poles in the murder of Jews during the Holocaust is still a powerful sentiment in contemporary Polish society. It was clearly reflected in the responses of leading public figures to the launching in Poland, less than three years ago, of the Wiesenthal Center's "Operation: Last Chance" project, which offers financial rewards for information facilitating the prosecution and punishment of Holocaust perpetrators. "We are a nation of victims, not perpetrators," was a popular refrain, while a former foreign minister whose father was murdered in Auschwitz reacted with "disgust and anxiety," and the editor of a prominent daily wrote of the dangers of the effort. GIVEN RADCZUK'S advanced age - 92 - Ronny Lerner is facing a daunting task. We will try our best to help him, but our success is not guaranteed. Yet Lerner's effort, which has identified and exposed a heartless Holocaust perpetrator many years after he committed his crimes, is nonetheless of great value, and a reminder that the annihilation of European Jewry was not a natural disaster, but a man-made catastrophe. The writer is Israel director of the Simon Wiesenthal Center.