[rudolf0]

And were any of these actually in positions of power to know definitively whether or not extermination programs existed (including ones not at their local camp)?

Also, how about Einsatzgruppen? Are there witnesses claiming they didn't exist either?

edit: Also, what's your response to the Wannsee notes and Posen speeches? Even if hypothetically the gas chambers never did exist, there's clear evidence they very strongly intended to kill all European Jews. Clear intent + 6 million Jews missing + a whole lot of mass graves seems like a pretty cut and dry case, even if you have to resort to saying they were all starved/worked to death and shot instead of gassed.