I've been google researching about grand juries. I'm not citing any links as I'm not sure which if any would be acceptable so this is just my take, MOO and nothing more. Grand juries serve two purposes, to advance criminal proceedings to the trial stage if an indictment is handed down and to protect citizens from frivolous prosecutions. At federal grand jury proceedings, the prosecutor is not obligated to present exculpatory evidence. This isn't always the case with state/local grand juries. In some states, prosecutors are required to present exculpatory evidence. I can't find anything that says whether or not MO is one of those states, but there is nothing that precludes prosecutors from presenting exculpatory evidence in any state if he or she chooses. Generally, a prosecutor, given the choice, would not present exculpatory evidence, but may choose to do so to gather further information from witnesses or to test how any exculpatory testimony plays before a jury. All MOO.