The ruling is due after four months of court hearings marked by victims' harrowing testimonies of the daily horrors at the death camp in occupied Poland.
Reinhold Hanning stands accused of complicity in more than 100,000 murders at Auschwitz.
Prosecutors say he had watched over the selection of which prisoners were fit for labour, and which should be sent to the gas chambers.
He is also deemed to have been aware of the regular mass shooting of inmates at the camp, as well as the systematic starvation of prisoners.
Prosecutors are seeking six years in prison as they argue that Hanning "contributed to the extermination aim of the camp".
But Hanning's lawyers want an acquittal, saying that the defendant had "killed, hit or abused no one".
The demand to free him has sparked outrage among survivors, with the International Auschwitz Committee calling it "macabre and outrageous".
Hanning was "part of the daily and omnipresent horrors that were meted out to all the Jewish families and other Auschwitz prisoners," said Christoph Heubner, the committee's deputy executive president, national news agency DPA reported.
'Silent all my life'
Hanning himself in April broke his silence on his time at Auschwitz 70 years after the war, telling victims "I am sorry".
He admitted to the court that he knew prisoners were being shot, gassed and their bodies burned at the death camp in occupied Poland.
But he said he had been "silent all my life" about the atrocities because he was ashamed, and had never spoken a word about it to his wife, children or grandchildren.
"No one in my family knew that I worked at Auschwitz. I simply could not talk about it. I was ashamed," said the white-haired, bespectacled widower, who owned a dairy store after the war.
"I want to tell you that I deeply regret having listened to a criminal organisation that is responsible for the deaths of many innocent people, for the destruction of countless families, for the misery, distress and suffering on the part of victims and their relatives.
"I am ashamed that I let this injustice happen and have done nothing to prevent it," he told the court.
More than one million European Jews were killed at the camp in occupied Poland, and among the 6,500 former SS personnel at Auschwitz who survived the war, fewer than 50 have been convicted.
Hanning's trial came on the heels of a high-profile case last year against Oskar Gröning, dubbed the "Bookkeeper of Auschwitz".
Gröning was sentenced in July to four years in prison, even though he had previously been cleared by German authorities after lengthy criminal probes dating back to the 1970s.
But the legal foundation for prosecuting ex-Nazis changed in 2011 with the German conviction of former death camp guard John Demjanjuk, solely on the basis of his having worked at the Sobibor camp in occupied Poland.
Another case is currently being heard by a German court, against former SS medic Hubert Zafke, 95, who is charged with at least 3,681 counts of complicity in killings.
Hearings have however been postponed on several occasions owing to the poor health of the defendant, raising questions on whether it can go ahead.