DON'T GET ARRESTED. Your role as a legal support person is vital for those who are arrested and you are much more use outside than in!
When people are arrested ask the senior police officer on site to let you know where they will be taken to be processed and also what charges they may be facing. Inform them (if you have been told to) of any medical issues arrestees may have. They may split up the arrestees or may take them to a distant police station for processing, so be ready to travel.