In what is likely to be one of Germany's last trials for World War Two-era atrocities, Reinhold Hanning was convicted last June by a judge who branded him a "willing and efficient henchman" in the Holocaust.
His lawyer, Andreas Scharmer, said he had found out about Hanning's death on Tuesday evening, but declined to comment on the cause of death beyond pointing to the man's advanced age.
Scharmer said the verdict against Hanning is not legally binding as appeals were still pending at Germany's highest court.
Thomas Walther, a lawyer for more than 20 joint plaintiffs in the Hanning case, said he was disappointed that Hanning had died before the conviction was binding, especially as he had expected the higher court to rule in the next month or so.
"If the judiciary had not been silent for decades, then there would not have been this disappointment," he said, adding he had expected the conviction to be confirmed.
A precedent was set in a similar case in 2011, when camp guard Ivan Demjanjuk was convicted, but he also died before the German Federal Court of Justice could rule on his appeal.
Hanning was silent and emotionless for much of his trial but at one point he did apologise to the victims and said that he regretted being part of a "criminal organisation" that had killed so many and caused so much suffering.
Hanning was not charged with direct involvement in any killings. But prosecutors and dozens of joint plaintiffs from Germany, Hungary, Israel, Canada, Britain and the United States said he had helped Auschwitz function.
(Reporting by Elke Ahlswede; Writing by Emma Thomasson; Editing by Stephen Powell)
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