A German judge ruled on Tuesday that it can no longer be proven whether a 105-year-old Dutch-born entertainer sang for Nazi guards at a concentration camp during World War II. Judge Michael Mauck dismissed a lawsuit by Johannes Heesters seeking a retraction and injunction against a German author and documentary maker, who has said the entertainer sang for SS troops at Dachau concentration camp in 1941. Author Volker Kuehn, who attended the hearing in a Berlin state court, welcomed the ruling as an "important signal." In some of his works, Kuehn cites a former Dachau inmate, who insisted he pulled the curtain for Heesters before the entertainer performed for the SS. Heesters took Kuehn to court in an effort to force him to retract the statements and prevent them from being further circulated. The court ruled there were "certain indications of a performance" by Heesters, but more than six decades later it is "no longer possible to clarify whether a performance took place."