Leuchter cited the absence of Prussian blue in the homicidal gas chambers to support his view that they could not have been used to gas people. However, residual iron-based cyanide compounds are not a categorical consequence of cyanide exposure. By not discriminating against that, Leuchter introduced an unreliable factor into his experiment, and his findings were seriously flawed as a result. In contrast, tests conducted by Polish forensic scientists (who discriminated against iron-based compounds) confirmed the presence of cyanide in the locations, in accordance with where and how it was used in the Holocaust. In addition, the report was criticized as Leuchter had overlooked critical evidence, such as documents in the SS architectural office which recorded the mechanical operation of the gas chambers and others which verified the rate at which the Nazis could burn the bodies of those gassed.