The above-mentioned and other inaccuracies in Reder's account of Bełżec also made this witness a favorite target of "Revisionist" propagandists.
Unable or unwilling to understand that – as every historian and trial judge knows – witnesses can be dead wrong about a great many details of events they describe (especially when it comes to highly violent, traumatic events) without this meaning that they are wrong about the events themselves, and that inaccuracies about numbers, measurements, technical mechanisms and other details in an eyewitness testimony merely mean that this testimony cannot be taken at face value and may be used only insofar as corroborated by other evidence, Hitler's willing defense attorneys often indulge in lengthy pleas against the testimonies of incriminating witnesses. Thomas Kues' Rudolf Reder’s Belzec – a critical reading is a textbook example of such exercise, complete with conspiracy theories suggesting or implying that Reder's account was influenced by that of Kurt Gerstein and later eyewitness accounts were contaminated by Reder’s account, possibly with some help from criminally corrupt interrogators trying to validate a pre-established story by obtaining "more tempered later accounts through a process of selection and coordination" that defense attorneys advised their hapless clients to go along with.
To be sure, much of the information provided by Rudolf Reder is badly mistaken. What this means from a historian’s point of view is that the same caution has to be applied in using Reder's account as evidence as is advised regarding the testimony of Kurt Gerstein, according to Christopher Browning:
Many aspects of Gerstein's testimony are unquestionably problematic. Several statements he attributes to Globocnik are clearly exagerrated or false, and it is not clear whether Gerstein or Globocnik was the faulty source. In other statements, such as the height of the piles of shoes and clothing at Belzec and Treblinka, Gerstein himself is clearly the source of exaggeration. Gerstein also added grossly exaggerated claims about matters to which he was not an eyewitness, such as that a total of 25 million Jews and others were gassed. But in the essential issue, namely that he was in Belzec and witnessed the gassing of a transport of Jews from Lwow, his testimony is fully corroborated by Pfannenstiel. It is also corroborated by other categories of witnesses from Belzec.
Just like the problematic aspects of Gerstein's testimony don't warrant completely dismissing him as a witness, the blatant mistakes in Reder's testimony don’t change the fact that Reder is remarkably accurate regarding some other details. Thus he described the Bełżec gassing engine as running on gasoline, which tallies with the testimony of Polish electrician Polish electrician Kasimierz Czerniak, as mentioned by German historian Peter Witte (regarding the claim of "Revisionist" engine expert F.P.Berg that gassing with gasoline exhaust would have necessarily implied "a telltale sign of carbon monoxide poisoning" inevitably noticed by witnesses, see the blog Interviews on American Freedom Radio and the discussion on the thead DEMJANJUK: Scapegoat for Jewish Madness starting with my post 11805). Comparison of a rudimentary map based on Reder's account with the results of Prof. Kola's archaeological investigation at Bełżec and of air photo analysis by Alex Bay shows that Reder was not that far away from physical evidence as concerns the number and approximate orientation of the mass graves, the placing of most graves roughly in the western-northwestern parts of the camp and the location of the graves in relation to the second phase's gas chamber building (details in the blog Belzec Mass Graves and Archaeology - Continuation (2)).
Another detail that Reder may have got at least partially right is his observation that "The gas was evacuated from the engine directly into the open air, and not into the chambers". For Kues this is "blatantly contradicting the later account found in Belzec which stipulates engine exhaust gas as a possible killing method". Mattogno (Bełżec or the Holocaust Controversy of Roberto Muehlenkamp) emphatically points out that
Gerstein moreover attributes the death of the victims in the alleged gas chambers to Diesel exhaust gas, while Reder asserts that the exhaust gases of his gasoline engine were vented not into the gas chambers, but into the open air!
In the blog Belzec Mass Graves and Archaeology: My Response to Carlo Mattogno (5,1), I argued that "Reder may have misunderstood the killing mechanism and for some reason wrongly assumed that the exhaust from the gassing engine was not introduced into the gas chamber. This would be an observation or recollection mistake such as often occur in eyewitness testimonies, which doesn’t exclude this eyewitness’s observations being correct in other respects, especially where corroborated by other eyewitness testimonies like concerning the type of engine." Another possibility is suggested by no less an authority on the subject than Erich Bauer, the Gasmeister of Sobibór, in one of his descriptions of the gassing process rendered on pages 101f. of Jules Schelvis, Sobibor. A History of a Nazi Death Camp (2007 Oxford International Publishers Ltd.). In his deposition on 6 October 1965 in Hagen (StA.Do-X'65-178), Bauer mentioned that
The chambers were permanently connected to the engine; the way it worked was that if a wooden plug was pulled out, the fumes went outside; if the plug was pushed into the pipe, the fumes went into the chamber.
Though it doesn’t become immediately apparent (at least to this writer, who is not an engine expert) what the purpose of this plug system was (maybe to have the engine running already as the gas chambers were being filled and start introducing the exhaust immediately after the doors were closed, rather than get the engine started only then), Bauer's description suggests that Reder at Belzec may have remembered the running engine prior to introduction of the plug, with the fumes going outside, but not realized that the fumes were then directed into the chamber by pushing in the plug. It should be noted in this context that Reder, as quoted by Kues, was uncertain about whether the engine killed by producing high pressure, by sucking air away or by introducing petrol exhaust that suffocated the victims.
This is just a hypothesis, for sure. But it seems to be one that deserves further study.