See trials: Nuremberg  Frankfurt Auschwitz Belsen Dachau  Zundel  Krakow Auschwitz
Between January 18 and March 10, 1972, two architects responsible for the design and construction of the crematoria in Auschwitz-Birkenau, Walter Dejaco and Fritz Ertl, were put on trial in Vienna, Austria.11 During the trial, an expert report on the possible interpretation of the blueprints of the alleged gas chambers of the Auschwitz and Birkenau crematoria was presented to the court. The report concluded that the rooms in question could not have been gas chambers, nor could they have been converted into gas chambers.12 Thanks to this first methodologically sound expert report on Auschwitz, the defendants were acquitted.  A Brief History of Forensic Examinations of Auschwitz by Germar Rudolf
I have had occasion to say that the real "Auschwitz Trial" was not that of
certain "Auschwitz guards" in Frankfurt (1963-1965), but the trial in Vienna, in
1972, of two men responsible for constructing the crematoria of Auschwitz, above
all those at Birkenau, Walter Dejaco and Fritz Ertl, architectural engineers.
Both were acquitted.
If the scantiest of the fragments presented here by Pressac (and, as he admits, already known at the time), could have proved the existence of homicidal gas chambers, this trial would have been played up with great fanfare and the two defendants been crushingly condemned. The trial, which was long and meticulous, and which was at first noisily heralded, above all by Simon Wiesenthal, demonstrated--as Pressac concedes--that the prosecution's designated expert was unable to trouble the two defendants; the expert "virtually admitted defeat" (p. 303). In July 1978 I paid a visit to Fritz Ertl (Dejaco had died that January), in hope that he could clarify certain points regarding the plans of the crematoria which I had found at the Auschwitz Museum. I discovered an old man, panicked by the prospect that his troubles were beginning anew. He was obstinate in refusing me the slightest information but he told me all the same that, for his part, he had never laid eyes on homicidal gas chambers either at Auschwitz or at Birkenau.
It is no secret that I would be delighted to have access to the documents from the pretrial investigation as well as the transcripts of the Dejaco/Ertl trial. I am convinced that these would include detailed answers on the architecture of the Birkenau crematoria, on their internal layout, on their purpose, and, lastly, on their possible modification. This Dejaco/Ertl trial, the preliminary investigation of which began in 1968 at Reutte (Tirol), is all too often forgotten: it prompted, for the first time, a general mobilization to prove the existence of homicidal gas chambers at Auschwitz. It marked the first time that the Soviet Union really played a role in furnishing valuable documents, and it witnessed the establishment of a sort of direct conduit between Moscow and Vienna through the intermediacy of Warsaw (Central Commission for the Investigation of German Crimes in Poland) and Auschwitz (archives of the Auschwitz Museum) (p. 71). Officials from the Jewish community throughout the world, alerted by Simon Wiesenthal, spared no effort. The two unlucky architectural engineers thus saw massive forces combined against them. Let it be added that, since they were quite unaware of the chemical and physical impossibilities of homicidal gassing in the facilities they had built, their plea was that the buildings' construction was perfectly normal, but that surely it was possible that certain Germans had used them to commit crimes. Dejaco went as far as to say: "And every big room could serve as gas chamber. Even this hearing room" (_Kurier_, January 20, 1972). Dejaco was greatly mistaken, since a homicidal gas chamber can only be a small room requiring a very complex technology and specific equipment, but nobody caught the error. It was during this trial (January 18-March 10, 1972) that the only Jewish "witness" to the gassings, the all-too-renowned Szlamy Dragon, "fainted" on the stand, and gave no further testimony (AZ, March 3, 1972). Pressac says that he demonstrated "total confusion" (p. 172). AUSCHWITZ: TECHNIQUE & OPERATION OF THE GAS CHAMBERS Or, Improvised Gas Chambers & Casual Gassings at Auschwitz & Birkenau, According to J.-C. Pressac (1989) by ROBERT FAURISSON