A former SS guard at the Stutthof Nazi concentration camp gave dramatic testimony about its gas chambers and crematoria on Friday, at what is likely to be one of the last Holocaust trials ever.

The 93-year-old Bruno D. described seeing people being led to their deaths in the gas chambers of the camp, and hearing their screams, while he stood guard in a watchtower, but added, "I didn't know that they were being gassed," according to news agency DPA.

The former guard is being tried in a juvenile court in Hamburg because he was 17 and 18 when he was deployed in the Nazi death camp, near the occupied Polish city of Gdansk, from August 1944 to April 1945.

He has been charged with being accessory to the murder of 5,230 people, but claims he did everything he could to avoid being sent to serve at the camp, after he learned he had a heart defect that prevented him from taking active service during the war. He said he tried and failed to be assigned positions in the Wehrmacht kitchens.

Facing questioning from the judge, Anne Meier-Möring, Bruno D. described seeing 20-30 people being led to the chambers. He said he couldn't be sure if they were men or women, because their heads were shaved, and that they did not resist before the doors were shut behind them.

He then heard banging and screaming from inside, followed by silence. "I didn't see anyone come out," he told the judge.

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'A place of horror'

Bruno D. also described seeing a group of prisoners being taken into the crematorium building by people wearing white gowns. He heard that they were to undergo a health examination before being sent on a work detail outside the camp, though he did not see them emerge from the building.

An expert witness from the state office of criminal investigation of North Rhine-Westphalia previously testified that there was an execution room in the crematorium, and that prisoners were deceived into entering the room before being shot in the back of the head. Bruno D. himself said earlier that he had seen several corpses stacked inside the crematorium.

Bruno D.'s testimony has now lasted more than a day and has been more lucid and comprehensive than that of the other nonagenarian men tried for their participation in the Holocaust in recent years. "I saw a lot of corpses," he said on Monday. "The images of suffering and horror followed me my whole life." He added that it was important for him to say that he was sorry for what had happened to the prisoners.

Listen to audio 00:15 Former concentration camp guard goes on trial

Although he described the camp as "a place of horror," D. insisted that he heard only "rumors" that the prisoners at Stutthof were political prisoners and Jews before being sent there. He said that he was never given a tour or information about the camp on arrival, and that his only orders were to safeguard "calm" in the camp and make sure no one approached the barbed wire fence.

He said he never used his gun during his deployment, and that when he, along with all the other soldiers, was given an SS uniform to wear, he was not given a choice. "No one asked: Do you want that? They said: You have to!" he was quoted by news outlet NTV as saying.

At one point during the trial, he was rebuked by the judge when he compared his own initiation in the camp, when he had to stand naked, to that of the prisoners.

The late Holocaust trials in Germany were only made possible by the precedent set by the conviction of John Demjanjuk in 2011, when a Munich court decided that working at a concentration camp constituted accessory to the murders that took place there. In a statement released in April, Hamburg state prosecutors said Bruno D.'s duties included the prevention of "escape, revolt and liberation" of the prisoners.

Up until then, German law stipulated that accessory to specific murders had to be proved, which meant that only a fraction of the guards at any of the Nazi death camps were ever brought to justice. The most notable of these was Oskar Gröning, who was found guilty of 300,000 counts of accessory to murder in 2015 for his employment in Auschwitz.