Rudolf Salomon Cortissos reached into his jacket pocket and pulled out a letter in a yellow envelope.

He unfolded the small piece of paper once, and then again, to reveal the neatly slanting handwriting of his mother, Emmy.

"We're with 2,500 people, and we're going to work," it read. "I promise you I'll be tough and I will definitely survive".

It ends with the words: "Thanks a lot for everything, hope to see you again."

The letter was dated 17 May 1943. Four days later, according to Red Cross records, she was dead, aged 31, gassed by lorry exhaust fumes at Sobibor in Nazi-occupied eastern Poland.

Today her son broke down as he tried to describe how Emmy had thrown the letter out of a train on her way to Sobibor death camp in the hope that someone would find it and send it to her family.

Cortissos, now 70 years old, was one of five relatives of some of the 250,000 Jews who perished in the death camp to deliver witness statements in the trial of John Demjanjuk, who is accused of acting as an accomplice in the murder of at least 27,900 who died at the camp during the five months he worked there in 1943.

"People were told they were going to labour camps," said David van Huiden,78, who lost his stepfather, his mother and his sister at Sobibor after they were rounded up by the Gestapo.

"They were told to pack warm clothes and decent shoes. But it was the biggest lie ever — You know what it was? A perfect door to door service. They picked you up at your home address, took you by tram to the train station and then to Sobibor. Once you arrived there, it was all over within four to five hours."

His family was murdered on 2 July, 1943. "It also happens to be my birthday," he told the court. Many were in tears.

Just metres from the witness box Demjanjuk, 89, who was deported from Cleveland, Ohio, in May to stand trial in Munich, lay passively on a stretcher, clad in a leather jacket and with blankets covering his body. A blue baseball cap concealed his entire face because of a ceiling light.

He has exercised his right to remain silent. Once, during the morning session the judge Ralph Alt, interrupted a lawyer to say: "Herr Demjanjuk wants to say something," when the retired carworker was heard to mumble.

"No, he's just praying," said his Ukrainian translator who leant over his bed throughout the day, whispering a continuous interpretation of proceedings into his ear. Demjanjuk then appeared to cross himself.

Another of five co-plaintiffs to deliver harrowing witness statements to the court said he did not discover what had happened to his mother, sister and brother until 10 years ago. "Part of me didn't want to know," said Martin Haas, 73.

Now a professor of biology and oncology in San Diego, Haas was sent to live with a foster family in the Dutch countryside when his family was rounded up. After the war when nobody came to pick him up he was sent to families around the country who were looking to adopt.

"I hated them all, until my father's second cousin found me, and he and his wife have been my parents ever since."

Mary Richheimer-Leyden van Amstel, 70, was the only survivor of her family.

She was just two when strangers agreed to hide her before her parents were herded to Sobibor. "I have no memories of anyone in my family," she told the court. "After the war nobody came to pick me up, and I just instinctively understood that my parents would not be coming back."

Demjanjuk's state of health — which his defence lawyers have tried hard to argue is not good enough for him to be able to stand trial — was once again the focus of much of the proceedings today.

His condition — he is suffering from a low-risk bone marrow complaint and other ailments — has enabled the defence team to present him as a victim, to the growing anger of the survivors of Sobibor as well as relatives of victims, many of whom are also suffering from frailty and poor health.

Kurt Gutmann, 82, who lost his mother and brother in Sobibor, was angry at the way that Demjanjuk had turned his illness into a courtroom drama.

"This is all made up," he said. "I myself have had three bypasses, but am I requesting a stretcher?"

Earlier in the trial Demjanjuk's lawyer, Ulrich Busch, elicited shocked gasps from the courtroom when he said the former Red Army soldier was as much a victim as the prisoners of Sobibor.

Efraim Zuroff, director of the Jerusalem office of the Nazi-hunting Simon Wiesenthal Centre, who was present to see the start of a case which he had helped bring to court, said it was in danger of focusing solely on Demjanjuk's health and not on the victims of Sobibor.

The trial continues with more co-plaintiffs due to give evidence tomorrow.

'I'll definitely survive'
Emmy Salomon was rounded up by the Gestapo in Amsterdam on 11 May 1943, when she went outside to get some fresh air because she feared an asthma attack was coming on. Her letter was written on 17 May 1943, just before her train left from Westerbork for Sobibor. She threw it out of the train somewhere on Dutch territory. Somebody posted it to the address on the envelope of the woman who was to look after her son, Rudolf.

According to Red Cross records, she was gassed in Sobibor on 21 May 1943.

Extracts from the letter read: "It is Monday evening, and we're ready to board the train. I promise you I'll be strong and I'll definitely survive … Nothing can be done about this.

"We're ready to board the train with 2,500 people [and we're] going to work …

"Take care of my husband, take care of my son, wherever he is …

"Thanks a lot for everything. I hope to see you again.

"Bye bye, Many kisses, Emmy."

guardian.co.uk