 In 1963 he embarked on the investigation for which he would become well known across Germany, unearthing important files for what became known as the second Auschwitz trial, which involved the arrest of the former camp commander, Richard Baer.Before and during the trial, which opened on 20 December 1963, Gnielka was able to testify regularly on the dreadful atrocities committed.However, he was diagnosed with skin cancer in 1963, and in 1965, before being able to complete his contribution to the court proceedings, he died.