Most people in Mississippi’s county jails have been locked up at least three months without formal charges while waiting to go on trial. Some have longer wait times because two-thirds of the counties only convene grand juries two or three times a year, according to a survey released Thursday by a group that tracks justice issues.

Mississippi does not require consistency among the 82 counties about how often grand juries meet to consider indictments — the formal charging documents needed to send a case to trial.