There has been a lot of publicity about grand juries due to the recent decisions involving police officers and homicides where the grand juries have decided not to move forward with indictments. Along with the publicity, there has been a lot of confusion about what grand juries do, how they do it and what they are actually deciding.
Grand juries are very different from the regular juries that participate in criminal trials. First, the few similarities. The people who make up grand juries and criminal juries generally come from the same pool in the community. They are both sworn to do their jobs, and they both listen to evidence. After that, there are significant differences. In a criminal trial, the jury gets to hear both sides, and each witness can be cross-examined by the other side's attorney. As a result, if a witness is not credible or changes his/her story, the other side's attorney will have an opportunity to question the witness, attack him/her with prior inconsistent statements and ask questions and present evidence that calls that witness's testimony into question. That is a key component to criminal trials. Both sides get to question the other side's witnesses to attack any areas the attorney believes is questionable, or an outright lie.
That does not really happen in grand juries. Both sides are not present in grand juries. Only the prosecutor is present to ask questions of witnesses in a grand jury proceedings, and he/she can be hard or easy on a witness depending on how that prosecutor wants the proceedings to go. The grand jurors can ask questions of witnesses, but they rarely do. Even if they want to, they are not likely to be experienced in cross-examination and do not have a full grasp of the evidence and the case to do a proper job of questioning a witness's credibility.
So, one critical distinction is that a grand jury witness can testify without the risk of the other side going after him/her to question the testimony. Many people have heard the statement, the prosecutor can indict a ham sandwich. Basically what this means is the prosecutor controls the grand jury proceeding. He/she can present whatever evidence he/she chooses, and more importantly, he/she can present that evidence in whatever biased manner he/she chooses. So, a prosecutor can present evidence in such a way that it looks very damning against a ham sandwich and without the benefit of the other side's attorney questioning that evidence, a grand jury is likely going to with the prevailing sentiment and decide to indict that ham sandwich. That is why the grand jury decides to indict approximately 99% of the cases they hear, according to statistics compiled by Nate Silver's FiveThirtyEight website. Of course, that 99% number only applies to regular people. When police officers are the subject of grand juries, that number goes down closer to 0%.
So, the inverse of the saying that a prosecutor can indict a ham sandwich is also true. A prosecutor can also fail to indict a criminal on any charges. It all depends on what evidence is presented, and perhaps more importantly, how the evidence is presented. As anyone who took any marketing class knows, context, delivery and presentation are critical components of persuasion.
Another key distinction is what the respective juries are there to do. Juries in criminal cases are empaneled to listen to all of the evidence from both sides and determine if the prosecution has proven that the defendant was guilty of the crime(s) charged beyond any reasonable doubt. This is a high standard. A grand jury is not there to decide if the defendant is guilty or innocent of a crime. The grand jury merely decides if there is sufficient evidence to charge the defendant so both sides can investigate further, prepare their cases and have their day in court. Practically, it is a preliminary decision that says the grand jurors think there is something to this and it should go through the normal criminal justice system process. And of course, how they are told that this is their job can certainly impact how they do that job and their ultimate decision. Make no mistake, if there is any evidence that a suspect committed a murder and you or I were that suspect, we would be indicted without delay, as that 99% figure suggests. That is true because grand jurors do not like to end murder cases or other serious criminal cases before they even go to court, and for regular people, the prosecutor is going to present that case to the grand jury in a way that encourages them to indict the case.
One final point about grand juries and high profile cases. Grand juries can be used as political tools for elected prosecutors who do not want to be held accountable for the difficult decision themselves. Different states have different rules about what cases must go to the grand jury in order for charges to be filed, but most cases do not need to be presented to a grand jury for criminal charges to be brought.
However, consider a situation where a case is getting a lot of publicity but to charge the defendant would be problematic for a prosecutor whether for political/election reasons or otherwise. The prosecutor does not want to make the decision to charge the suspect because it might upset certain large voting blocs. On the other hand, the prosecutor also knows it would look bad for him/her to just drop the charges on his/her own. The grand jury is perfect for this scenario. The prosecutor can convene a grand jury which meets secretly in a private room where the prosecution can present whatever evidence they want in whatever manner they want. The prosecution can steer the grand jury in the direction it chooses. When the grand jury decides not to indict the suspect, the prosecutor can get up in front of the media and disclaim any responsibility for the decision and defer to the grand jury. Since the other side had no representatives in the grand jury, the other side could neither attack the witnesses presented nor give their side to try and get an indictment. For that reason, the grand jury is the perfect responsibility-shifting method to get the desired result without taking any of the blame when election time comes back around.