A 96-year-old former Auschwitz guard who was convicted for his role in the murder of 300,000 Hungarian Jews and ordered to serve four years in prison has filed a new request for clemency.

Oskar Groening late last week asked the Justice Minister of Lower Saxony, the northern German state where his 2015 trial took place, to pardon him so that he does not have to go to prison. Lower Saxony Justice Minister Barbara Havliza can take as much time as she wants to make the decision.

A clemency plea filed with German prosecutors was rejected in January.

He had been expected to enter prison at the end of January, but the continued wrangling over the state of his health has kept him from beginning to serve his sentence.

Groening, known as the “bookkeeper of Auschwitz,” was convicted and sentenced in July 2015 for his role in the murders of Hungarian Jews at the concentration camp in Nazi-occupied Poland. A federal appeals court rejected his appeal a year ago. He had remained free while waiting for a determination of his fitness to serve time in prison after requesting that the sentence be suspended.

Germany’s constitutional court, the country’s highest court, rejected Groening’s appeal, ruling in December that he could receive appropriate health care in prison, and that his jail sentence could be “interrupted” should there be a change in the nonagenarian’s health.

Groening had admitted to being tasked with gathering the money and valuables found in the baggage of murdered Jews and handing it over to his superiors for transfer to Berlin. He said he had guarded luggage on the Auschwitz arrival and selection ramp two or three times in the summer of 1944.

During the trial, Groening asked for forgiveness while acknowledging that only the courts could decide when it came to criminal guilt.