Purpose is to ensure D will appear at trial. Denial of bail when right exists may be a violation of due process. Preventive detention is consitutional. Grand jury 5 th Amendment right to grand jury not applied to states. Some states use grand juries anyhow.
Grand juries are secret, and D has no right to notice or to call witnesses.
No right to counsel. No right to have illegally obtained evidence excluded. Witness may take the 5 th . Exclusion of minorities is about the only grounds for quashing a grand jury indictment. Attaches when D is arrested or charged.