On Tuesday, 70 years after the liberation of Auschwitz during World War II, the trial of a 93-year-old former Nazi guard at the camp started in Germany.

Oskar Groening, one of the last remaining Nazi SS members alive, stands accused of his role in the Holocaust. He spoke at the opening of the court proceedings to admit a moral guilt, but added that prosecutors would have to determine his legal culpability.

"I ask for forgiveness," he told the judges. "I share morally in the guilt but whether I am guilty under criminal law, you will have to decide."

Groening, who was known as the "bookkeeper of Auschwitz," is charged with some 300,000 counts of acting as an accessory to murder. The Nazis killed at least 1.1 million people, mostly Jewish victims, at the concentration camp.

The former guard appeared in a 2005 BBC documentary, Auschwitz: The Nazis and the Final Solution, in which he acknowledged witnessing the systematic slaughter and abuse of prisoners at Auschwitz, where his job was to collect the money they brought with them.

"I saw the gas chambers. I saw the crematoria. I saw the open fires. I was on the ramp when the selections [for the gas chambers] took place," Groening said in the film, speaking out against Holocaust denialism. "I would like you to believe these atrocities happened — because I was there."

Fourteen survivors are expected to testify in what could be a months-long trial, one in which Groening himself is expected further discuss his role in the Holocaust.

That Groening is not accused of directly murdering anyone but is being prosecuted for his complicity is a recent development in how Germany is investigating and prosecuting crimes from the war, according to Lawrence Douglas, an Amherst College law professor and author of a forthcoming book about the last major Nazi prosecution, The Right Wrong Man: John Demjanjuk and the Last Great Nazi War Crimes Trial.

"For a long time the German legal system wasn't even about to try to people like Oskar Groening, but that changed with the Demjanjuk conviction, which made possible a new legal theory to try relatively low-level guards," he told VICE News.

John Demjanjuk had been living in the United States when he was extradited to Israel in the 1980s to face trial for being identified as a bloodthirsty guard at Treblinka extermination camp in Poland known as "Ivan the Terrible." Though convicted, Israel's Supreme Court later acquitted him on new evidence in 1993.

But Demjanjuk spent much of the following decade in court fighting deportation to Germany on new charges of his role as a guard at the Sobibor extermination camp. He was ultimately extradited and convicted in 2011 as a 91-year-old accessory to the murder of 28,000 people. During his 18-month trial, he often appeared in a wheelchair and sometimes lying down. Demjanjuk was sentenced to five years in prison and died while awaiting appeal, which had the quirk of invalidating his conviction under German law.

After Demjanjuk's case cleared the way for other prosecutions of low-level participants in the Holocaust, prosecutors moved to aggressively pursue alleged offenders while they were still alive. They reopened about 30 cases but found that only about three could go forward, Douglas said — one of which was Groening's.

"It's the 11th hour," Deborah E. Lipstadt, a Holocaust scholar at Emory University, told VICE News, referring to the fact that such offenders will not be around for much longer. "There are those who argue that these are old men — leave them alone, don't bother them — but it's important to remember that they went after old men and little babies, all sorts of people who couldn't defend themselves. It's part of justice."

Groening "has openly acknowledged serving as an SS officer," she noted. "His forthcomingness will probably be taken into account by the court."

The defendant has been applauded for his willingness to admit his role and prove Holocaust-deniers wrong. Both Douglas and Lipstadt said that this would likely make a difference in his trial.

"Oskar Groening is actually going to testify," Douglas said. "There is a very famous line, from a German Jewish DA back in 60s, who during a [Holocaust] trial said that he waited for one humane word to be uttered by the defendant, and that one humane word would have changed everything. So it will be quite interesting to see whether Groening, who has been open about his participation, makes a moving and interesting and reflective statement."

The trial will be overseen by three judges and two lay "assessors" who act somewhat analogously to jurors but with less input into the final decision on guilt, Douglas explained. He noted that it will be the latest of only a small number of prosecutions of members of the Nazi party over the 70 years since the war ended.

"In the postwar period Germany had very little enthusiasm for trying former Nazis," Douglas said. "Not to engage in a super simple explanation, but the fact of matter is, in the postwar years the German judiciary was stocked with former Nazis, and there was very little inclination or desire to bring these cases forward."

In the intervening years, there have been thousands of investigations by the Central Office, Germany's investigatory body, but they only resulted in a "very small number of trials, and of that small number, an even smaller number of convictions," Douglas said. "That [Germany] continues to have trials 70 years after the fact reminds us how fraught that history is, how ongoing the struggle to comes to term with that history remains."