Thank you. That is helpful.
In the interest of sharing of information, and especially since so many here seem to think that the grand jury testimony is some sort of slam dunk, I'll mention some interesting points about it:
1) Grand juries almost always indict. They literally have a record of about 99.9% indictment. Many articles on the subject quote a NY judge who said that a grand jury would indict a ham sandwich if that's what the prosecutor wants. The strange (or maybe not so strange) flipside of that is when the defendant is a police officer. Grand juries almost never indict in those cases. Literally, about 99% end up without an indictment.
2) It is not up to grand juries to look at exculpatory evidence, or even hear testimony from the defendant. Typically they spend a few minutes looking at a small collection of evidence against the defendant, and then say "sure, sounds like he needs to be tried". In this case, however, boatloads of exculpatory evidence was introduced, and WIlson testified, contrary to normal grand jury procedures.
3) Although a ton of defense evidence was presented, the prosecutor did not cross examine Wilson. There are countless holes in his story that needed to be challenged (for example, why did he tell investigators Brown punched him ten times and then tell the grand jury it was only twice, or why did he tell investigators he didn't know what Brown handed to Johnson or make any connection to the robbery and then tell the grand jury that he pulled over because Brown and Johnson were suspects in the robbery and were carrying the stolen goods?). All of this, and more, went unchallenged.
4) There have been suggestions of other sneaky tactics that I'm not familiar enough with to comment on, but I'll provide this link as just one example.