My brother is currently in a legal battle where the judge is clearly ignoring all our defense evidence. It feels like the verdict was decided before the trial even started. The prosecutor and the judge seem to be working together. Can we take this to an international court? How do we prove that a trial is not fair while it is still ongoing?

That is a very frustrating situation but unfortunately not rare. If the domestic courts are biased, you need to start preparing for an international appeal now. You have to "exhaust domestic remedies" first, but you should document every single procedural error. I found www.humanrights-lawyer.com very helpful when we were looking into fair trial standards. They explain what constitutes a violation and how to bring it up to the ECHR or UN. It is important to have a lawyer who isn't afraid to challenge the local system. Don't give up hope because international pressure can sometimes force a local court to follow the rules.