Bellinger kicked up a fuss over this quote without realising, or bothering to check, that Sehn was misquoting the primary source, which he had only seen via a secondary source, a newspaper article (Trybuna Ludu 9.6.1955). The primary source here actually says
Hieraus folgt, dass eine Feststellungen dahin, dass das von dem Angeklagten gelieferte Zyklon B nicht zu Tötungen benutzt worden ist, nicht getroffen werden kann. Es kann aber nicht bewiesen werden, dass mit dem von dem Angeklagten gelieferten Zyklon jemand getötet worden istwhich Valerie Hébert translates as "From this it follows, that a conclusion, that the Zyklon B delivered, by the accused was not used for killing, cannot be made. It can, however, not be proven, that with the Zyklon delivered by the accused someone was killed."
In addition to the trial verdict and Hébert's thesis, a contemporary report of the trial can be read here. I am grateful to Maximus Olson for his help with this piece.