A German woman dubbed the “Nazi grandma” was sentenced to 10 months in jail for Holocaust denial.

Ursula Haverbeck told a court in Hamburg last week that the Nazis’ Auschwitz death camp is “only a belief.”

Haverbeck was charged in April with Holocaust denial after calling the Holocaust in a statement broadcast on television ”the biggest and most sustainable lie in history.” She made the statement to reporters outside of the trial of former SS guard Oskar Groening.

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Groening was convicted in July as an accessory to the murder of 300,000 in Auschwitz.

Haverbeck challenged the court to prove that Auschwitz was a death camp, the German Deutche Welle reported. She was sentenced on Nov. 12.

Magistrate Bjoern Joensson, who issued the sentence, said it is “deplorable that this woman, who is still so active given her age, uses her energy to spread such hair-raising nonsense.”

“She is a lost cause,” he added, according to Deutche Welle.

Haverbeck already has a criminal record, including two fines and a suspended sentence for sedition. She said she will appeal the sentence.

It is illegal in Germany to deny or downplay the Holocaust.