The former SS guard Oskar Gröning, who is accused of complicity in the murder of 300,000 Hungarian Jews, has admitted guilt for his role in the Nazi killing machinery, but said he had no right to ask for forgiveness.

Gröning, 94, told a court: “I’ve consciously not asked for forgiveness for my guilt. Regarding the scale of what took place in Auschwitz and the crimes committed elsewhere, as far as I’m concerned I’m not entitled to such a request. I can only ask the Lord God for forgiveness.”

Gröning – called the Accountant of Auschwitz because he was tasked with sorting through Jews’ possessions, and collecting and counting the money found in suitcases and clothing – also revealed for the first time the profound emotional impact the testimonies of Auschwitz survivors and their relatives had made on him.

“The events of Auschwitz, the mass murders, were known to me. But many of the details that have been told here were not known to me,” he told the court in Lüneburg, northern Germany, through his lawyer.

Irene Weiss, who testified of her experience at Auschwitz, arrives for the trial of Oskar Gröning. Photograph: Ronny Hartmann/AP

“What happened in Auschwitz has been brought before my eyes once again. The suffering of the deportees in the trains, the selection process and the subsequent extermination of the majority of the people has been brought home to me again in the clearest possible way … as well as the terrible living conditions of those who were not murdered immediately.”

His declaration gave the court its first insight into Gröning’s emotional state since the trial began in April. Gröning said it was “with regret and humility that I stand before the victims”. But he repeated his earlier claims that he had only served on a selection ramp a handful of times – the rest of the time he had been in an office counting prisoners’ money – that he had tried to get transferred to the front several times and that he had never killed anyone.

“In 1943 … my fiancee and I wanted to get married,” he said. “We also planned to have children, but it seemed to me incompatible to plan a family and to continue working in Auschwitz, so I reminded my superiors of my wish to transfer.” He told the court he believed his application was never processed.

Gröning’s 15-minute declaration was followed by the powerful testimony of Irene Fogel Weiss, an 84-year-old retired teacher from Fairfax, Virginia, who described in detail how her family was torn apart on arrival at Auschwitz in May 1944 during the mass deportation of Hungarian Jews. Weiss lost both her parents, four siblings and 13 cousins at Auschwitz.

Looking directly at Gröning, who was seated just 20ft from her, she said: “He has said that he does not consider himself a perpetrator but merely a small cog in the machine. But if he were sitting here today wearing his SS uniform, I would tremble, and all the horror that I experienced as a 13-year-old would return to me.

“To that 13-year-old, any person who wore that uniform in that place represented terror and the depths to which humanity can sink, regardless of what function they performed. And today, at the age of 84, I still feel the same way.”

Gröning looked on passively, occasionally gazing at the ceiling and sipping from a bottle of water as she spoke.

Weiss described in detail her family’s deportation from their home in Hungary to Auschwitz, recalling how the mayor, police chief and her headteacher knocked on the door of the family house one morning in April 1944 to escort the family to a makeshift ghetto in an abandoned brick factory.

“They demanded our valuables, and my father gave them some money and jewellery,” she told the court. “We left our house, my father closed the gate behind us so our dog wouldn’t follow.”

The court was shown a coloured photograph discovered in the early 1970s, showing a mass of prisoners gathered at the selection ramp, Weiss clearly visible in her winter coat and headscarf in the bottom left hand corner, “standing there looking in the direction where my little sister went … I did not move, trying desperately to see if she had caught up with my mother,” she said.

“This is the picture that was burnt into my mind for the last 70 years,” she said, pointing at the image which was beamed up on a large screen in the courtroom.

Irene Weiss holds a photo of her that was taken at Auschwitz by two Nazi guards. Photograph: Jocelyn Augustino

Her father and 16-year-old brother had been sent to dispose of dead bodies. She later discovered, in a note passed to her by another prisoner, that her father had been shot shortly after his arrival. She never discovered her brother’s fate.

Weiss and her sister, Serena, were sent to work near crematorium No 4 at a storage and processing area known to the prisoners as “Kanada”, to sort through the belongings of those who had entered the camp.

“There we sorted through mountains of clothing, shoes, bedding, eyeglasses, toothbrushes, baby carriages, suitcases, books, pots and pans, and every other household item,” she said. “While at work one day I found my mother’s white dress and beige shawl.”

She said the task was overwhelming as trainloads of prisoners continued to arrive around the clock. “The piles never became smaller. The piles reached as high as the roof of the barracks,” she said.

The trial is tentatively expected to conclude later this month.