In most cases, a jury will consist of 12 main jurors and 1 or 2 alternates. This applies in most civil cases and criminal cases in most states. The alternates usually sit through the trail, so they can hear all the evidence present, and be able to fill in if one of the main jurors gets sick or cannot continue for whatever reason.
In a Mississippi civil case, the decision (verdict) of the jury need only be reached by 9 out of the 12 jurors. In a Mississippi criminal case, the decision must be unanimous, meaning all 12 jurors must agree to convict. For more information on Mississippi courts, click here. Other states have different rules.