Johann Breyer, who was born in Czechoslovakia and has lived in the United States for 62 years, was arrested late Tuesday at his Philadelphia home. He appeared in federal court the next morning in chains.
Investigators say that Breyer joined the Waffen SS at the age of 17 and served as a guard at Auschwitz, assisting in the killing of Jewish people and others in the gas chambers. He avoided deportation in 1992 by arguing that he had been born a U.S. citizen because his mother held citizenship.
Breyer could be the last person to be arrested in the United States for his part in Nazi atrocities during the Holocaust.
At Wednesday's hearing, his lawyer said that Breyer has mild dementia. But Magistrate Judge Timothy Rice said that Breyer appeared to have adequate understanding of the court proceedings.
A German indictment was unsealed Wednesday.
Breyer allegedly worked at Auschwitz II or Birkenau, part of a network of camps in what was then the German province of Upper Silesia. Birkenau was primarily a death camp.