Now put yourself in the prosecutor’s shoes. You have a case in which the only evidence against the accused is discredited, and you know it’s going to be discredited. So to take Wilson to trial would not just be unjust to Wilson. It would be prosecutorial misconduct. A prosecutor can get in a lot of trouble for trying to take a case to court based on evidence he knows to be unreliable. Ask Mike Nifong.
So what is McCulloch supposed to do? He could declare that he isn’t even going to take this case to the grand jury. But that wouldn’t create the kind of paper trail that we can all pore over, as we are doing right now, to determine whether there was a case or not. Sure, there would be forensic reports and police interviews. But these would be easier for people to dismiss as self-serving lies told by the cops. Instead, taking the case to the grand jury and giving them everything was a good way for McCulloch to approximate the kind of presentation of evidence that would happen in a trial and to have it all available as a matter of public record through a semi-independent process.
McCulloch must have known that he wasn’t going to win this one. No matter what he did, the rioters were going to riot, because they had already made up their minds and had their own, pre-existing ideological motivations. He was trying to choose the least bad option. In that respect, simply declaring he wouldn’t pursue the case would make it seem too much like a unilateral police cover-up. (McCulloch comes from a family of cops and has been accused in the past of being too reluctant to prosecute officers.) So using the grand jury process to introduce all of the evidence was the best option left. It wouldn’t stop the rioters, but at least it would help get all of the facts out.