BERLIN—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 …