Understanding eyewitnesses, is crucial to correct interpretation of their testimony. Without understanding, any interpretation is likely to be inaccurate.
https://www.sciencedirect.com/science/a ... 1325000270
"Many believe that eyewitness memory is unreliable, but a better way of thinking is that eyewitness memory, like other types of forensic evidence, can be contaminated. Because contaminated evidence yields unreliable results, the focus should be placed on testing uncontaminated memory evidence collected early in a police investigation. The recent application of theories, principles, and methods from cognitive science has revealed that, both in the laboratory and in the real world, the first test of uncontaminated memory provides much more reliable information than was previously thought"
https://www.scientificamerican.com/arti ... s-have-it/
"Many people believe that human memory works like a video recorder: the mind records events and then, on cue, plays back an exact replica of them. On the contrary, psychologists have found that memories are reconstructed rather than played back each time we recall them. The act of remembering, says eminent memory researcher and psychologist Elizabeth F. Loftus of the University of California, Irvine, is “more akin to putting puzzle pieces together than retrieving a video recording.”"
So-called revisionists refuse to recognise the issues with memory and recall, preferring to claim, with no evidence, that those issues prove lying. Reder is given as an example of an unreliable witness, which is correct, but that does not therefore mean he lied about what he saw, or what he was told about at Belzec. The majority of what he related, about the process at the camp and for gassings, is corroborated. For example;
https://www.jewishgen.org/yizkor/schind ... dendum.pdf
"I was a member of the permanent death commando. We were 500 men all told."
The use of trusted labourers, to work at the gas chambers, is reported from every single death camp. That claim is corroborated and so proven. Reder's estimation of there were 500 of them, is an estimation. It is likely wrong, as it has been established he made a series of unreliable estimations. That does not make him a liar.
He escaped from Belzec in 1942, and wrote his testimony in 1945-6. That means he is relying on his memory and as shown above, studies have proved memory can be contaminated and that is fragmented and has to be reconstructed. It is easy for him to remember a detail such as he was tasked to work as a "death commando". It is harder to estimate how many of those workers there were. A witness is not lying, if they remember one thing correctly and another not.
"There were mass graves on both sides of the building housing gas chambers.
Some were already full; others were still empty. I saw many graves filled to
capacity and covered high with sand. It took quite a while for them to level
down. There always had to be one empty pit… just in case’"
Archaeological surveys corroborate that claim. A series of mass graves, were located using a borehole survey, and not all of the boreholes found any remains. He makes no estimation, and remembering graves is a simple memory, easily retained. That the physical evidence corroborates him, proves he is not lying about the presence of mass graves.