But on top of that, it has to be proven in cases where the posts contain illegal content that the moderation/administration staff have seen and ignored it and are therefore allowing such content to remain on their site, or have simply not gotten around to reviewing that content
Now I know I'm not a lawyer but "Innocent until proven Guilty" is still a case in the modern day court of law, and therefore if you can prove (which is now easier with database marking in 3.5) that you haven't read that thread at the time of it being reported, then you can be excused from any responsibility
Chris