He worked from 1980 till 1989 for the East German secret police under the pseudonym IM "Schubert".
In March 2008 Singer has won an interim injunction to prevent an exhibition in Reichenbach from including his name and clandestine activities.
On April, 22 he "lost a legal bid to keep his identity from being made public" and the injunction was cancelled.
In March 2010 the court finally decided that the exhibition maker can make the real name of "IM Schubert" public.
"The activity of the IM, who had repeatedly admitted his past deeds", said the acting judge, was "of historical interest".