Grand Jury Resisters

Okay comrades i have a basic understanding of this "GJR" thing.. Police took people in custody for some crime and they are refusing to speak to the grand jury which is a jury who decides if people should be charged or not before going on to a "real" court where they decide if they are guilty or not guilty? Do i have it right? Could someone elaborate and explain it in detail?

no, the grand jury collects supposedly evidence against others, so the people now in jail got summoned to testify about other anarchists/activists, supposedly about their involvement in some broken windows of an federal courthouse during mayday (but that is a. secret, so we dont know for sure and b. the GJR said the questions where almost all about mapping the wider anarchist movement, not what happened on mayday).
the people summoned (and now in jail for refusing to testify/snitch) where offered immunity so they are not in jail because they want to not incriminate their selves, they are in jail because they refuse to co-operate with an political prosecution of others.
there are a bunch of articles that explain the grand jury system and how its a sneaky work around normal juridical procedure in layman terms in this thread; http://www.revleft.com/vb/grand-jury...164/index.html