Craig Murray has been covering this trial from the public gallery. He certainly has his opinions and I don't want to get in the weeds on that account. He did mention that very few people were allowed in the public gallery, the rest where to sit in a room next door where (he claims) the sound is difficult to hear.[0]

My understanding at this point is that the public isn't really allowed access at all. The poor sound quality makes it impossible to understand what is happening, it's not access in the sense that they can follow the proceedings. Craig Murray seemed to be saying that Amnesty International was excluded even from this room. I believe this may be the crux of Amnesty International's complaint.

"Rather to our surprise, nobody else was allowed into the public gallery of court 10 but us five. Others like John Pilger and Kristin Hrafnsson, editor in chief of Wikileaks, were shunted into the adjacent court 9 where a very small number were permitted to squint at a tiny screen, on which the sound was so inaudible John Pilger simply left. Many others who had expected to attend, such as Amnesty International and Reporters Without Borders, were simply excluded, as were MPs from the German federal parliament (both the German MPs and Reporters Without Borders at least later got access to the inadequate video following strong representations from the German Embassy)."

[0]: https://www.craigmurray.org.uk/archives/2020/09/your-man-in-...