Thomas Blatt, one of the few inmates to escape from the Nazi death camp at Sobibor, began his testimony Tuesday at the trial in Munich of John Demjanjuk, alleged to be a former camp guard, DPA reported.
"I'm not after revenge. I only seek justice," Blatt, 82, told the reporters just before he went into the German courtroom.
He and fellow witness Philip Bialowitz, 84, took part in a mutiny in October 1943, fled over the fence and managed to go into hiding. Three trial days have been set aside to hear their accounts.
The Nazis had not sent the young men straight to their deaths in the Sobibor gas chambers but were using them as slave labourers. Both have said on many occasions that they cannot remember Demjanjuk's face or name.
Demjanjuk is accused of being an accessory to the gas-chamber murders of 27,900 Jews in the period in 1943 when he was assigned to the camp by the SS.
Blatt said outside the court he was not focussed on punishment but on finding the truth.
"This will be important historically 200 years from now," he said.
Bialowitz also stressed the historical dimension, saying, "I'm heat to tell what Sobibor means."
Both men are private co-prosecutors at the trial, because their direct relatives were murdered in Sobibor.
Demjanjuk's lawyer, Ulrich Busch, who has opposed the trial with a series of unsuccessful motions, challenged the lawyers appearing for the two former escapers. He said they were not entitled under German law to appear as counsel because they had previously been involved as government officials in inquiries against Demjanjuk.
Judges said they would consider Busch's objection later and went ahead with hearing the testimony.
As a skinny 15-year-old from the Jewish village of Izbica, Thomas Toivi Blatt was picked by the Nazis for slave labour and lost his parents and younger brother in the Sobibor gas chambers.
Earlier this year, Blatt explained why the trauma of his experience meant he could not remember the faces of the guards, saying, "I can't even remember the faces of my parents and brother."
About 50 inmates managed to get away in the October 1943 inmate revolt, which prompted the camp closure. A farmer shot at him during his flight, and he still has the bullet in his jaw, he said.
After the Second World War ended in 1945, Blatt initially returned to Poland, then moved to Israel, then to the United States in 1959 with his American wife. He has been active for many years writing and lecturing about the Holocaust.