(L - R) Richard Baer, Josef Mengele, Josef Kramer, Rudolf Hoess, and Anton Thumann, at the SS retreat Solahütte in 1944.
Below is a photograph of a 49-year-old Richard Baer following his capture near Hamburg in December 1943.
A photo of the cabin in which he'd lived since the end of the war.
German judge Wilhelm Stäglich wrote in his 1979 study Auschwitz: A Judge Looks at the Evidence:
Particularly noteworthy is the fate of the most prominent of the defendants, Richard Baer, the last commandant of Auschwitz. He did not live to see the beginning of the [Frankfurt-Auschwitz] trial. In December of 1960, Baer was arrested in the vicinity of Hamburg, where he was employed as a lumberjack. He died in June of 1963 under mysterious circumstances while being held in pre-trial custody.
According to various sources, which, in turn, rely on reports that appeared in the French press, Baer adamantly refused to confirm the existence of "gas chambers" at the camp he once administered.* Although it has been alleged that he was eliminated by poisoning on account of this refusal, the cause of his death has never been established. His wife claimed that he was in excellent health.
While Langbein merely states that an autopsy revealed that he died of "natural causes,"Naumann specifies a "circulatory ailment" as the cause of death. Of course, a circulatory ailment is only a symptom of preexisting disease that has causes of its own. It is quite possible, however, that the physical condition of this strong and healthy outdoor labourer deteriorated as a result of his treatment in prison. That would be damning enough to those suspicious of the whole affair when one reads the report on the autopsy performed at the Frankfurt-Main University School of Medicine: "The ingestion of an odourless, non-corrosive poison... cannot be ruled out." Nevertheless, there was no further probe into the cause of Baer's death, and Chief Public Prosecutor Bauer ordered his body cremated. One may dismiss the possibility that Baer committed suicide, since, according to his wife, he was counting on an acquittal. Moreover, shortly before his death Baer complained to the guards that he was feeling ill and asked for a physician. That is hardly the action of someone who intends to take his own life.
This very mysterious event hardly attracted public attention, and presumably the affair was systematically hushed up. When one considers the reaction the death of an inmate in a German prison usually calls forth among officials, legislators, and the mass media, it seems astounding that this case was kept so quiet, all the more so because Baer was no ordinary prisoner, but a man whose testimony could have had the greatest impact in the upcoming trial.
* The aforementioned [Herman] Langbein—an Auschwitz survivor, communist, and prominent Holocaust writer; who testified at the Frankfurt-Auschwitz trial—was one of the editors of the supposedly authoritative volume Nationalsozialistische Massentötungen durch Giftgas: Eine Dokumentation, first published in 1983 (i.e. 4 years after Stäglich published the above). The following is taken from the 1993 English translation (p. 142):
Richard Baer, the last commandant of Auschiwtz I, who died in Frankfurt during the hearings that preceded the Auschwitz trial there, stated on 22 December 1960: "I commanded only Camp I at Auschwitz. I had nothing to do with the camps where gassings took place. I had no influence over them. It was in Camp II, at Birkenau, that the gassings took place. That camp was not under my authority."
The cited source is:
StA Frankfurt a/Main AZ: 4 Js 444/59, vol. 42, p. 7409 (ZSL: AZ: 402 AR-Z 37/58).