A former SS guard, now 101 years old, denied on Thursday he had worked at the Sachsenhausen concentration camp, a court spokesperson said, dragging out his trial on charges of helping to send more than 3,000 people to their deaths.
Prosecutors say Josef S., a member of the Nazi party's paramilitary SS, contributed to the deaths of 3,518 people at the Sachsenhausen camp by regularly standing guard in the watchtower between 1942 and 1945.
Doctors have said the man, whose full name was not disclosed due to German trial reporting rules, is only partially fit to stand trial: sessions will be limited to just two and a half hours each day.
Josef S. shielded his face from cameras behind a blue binder as he faced the court in Neuruppin, near Berlin, to testify.
"Today, the accused stood by his overall account that he had not worked in the Sachsenhausen concentration camp," said court spokesperson Iris le Claire.
The co-plaintiff's lawyer Thomas Walther said: "The historian must now painstakingly prove this (that he was at Sachsenhausen) by providing an expert opinion, with success."
Some people interned in Sachsenhausen were murdered with Zyklon-B, the poison gas also used in other extermination camps where millions of Jews were killed in the Holocaust.
Sachsenhausen housed mainly political prisoners from across Europe, along with Soviet prisoners of war and some Jews.
There has been a spate of charges brought against former concentration camp guards in recent years for World War Two crimes against humanity. In September, a former camp secretary went on the run the day her trial was to begin, but was caught by police hours later.
A 2011 court ruling paved the way for these prosecutions, stating that even those who contributed indirectly to wartime murders, without pulling a trigger or giving an order, could bear criminal responsibility.