Here's what a lot of people are missing, both for the Michael Brown and for this case:
There is no double jeopardy for grand jury trials.
All of the people yelling and screaming for a full trial in either of these cases? You're arguing for the cops in these cases. You don't think you are, but you are. Because if the case is so weak that it's fucking possible for the prosecutor to "throw the case" and not get an indictment out of a grand jury, the defense would have to have a monumentally stupid lawyer to not win an actual trial. And once that happens, Game Over. No more re-trials. No more prosecution. Nada. Zip. Nothing.
For fuck's sake, did you not learn anything from the Zimmerman case of last summer? DON'T TRY A CASE UNLESS THE GRAND JURY GIVES YOU AN INDICTMENT. A grand jury is looking for 50%+. A trial jury is looking for 99%+. If you can't clear the 50%+ mark (which is why Angela Corey skipped the Grand Jury and that's how the Zimmerman case was actually lost by the prosecution), then you're dead meat when it comes to clearing the 99%+ bar.
In the Michael Brown case it was pretty damn clear from the outset that there wasn't enough to get a conviction. It would take smoke and mirrors to get an indictment, let alone a conviction. Yes, the prosecutor COULD have gotten an indictment if he really, really spun it. And then what? Wilson goes 100% free after the trial, after millions of dollars are spent both on his lawyers and on the prosecution and the circus of the trial, all for a dead case that would have 0% chance of winning.
Not getting in indictment means the prosecution can still keep digging for more information, for more witnesses, and keep trying.
Do I think they're going to? No. Because unless some new evidentiary bombshell drops, which I don't happen to think is likely, the Brown case is done. But if a video comes out that shows Brown with his hands up and meekly obeying orders when Wilson shoots him dead, not going to trial means you can still prosecute Wilson. If you went to trial, Wilson was found not guilty, and THEN you find the video, Wilson stays free. Double jeopardy. At that point, he's immune on murder charges.
Is any of that getting through to you people? Yes, the prosecutors are chickening out. They're chickening out the SMART way, by leaving their options open (which Angela Crowley didn't, in a fit of grandstanding stupidity). while also not wasting time, money, and effort that would be better directed towards cases the could be WON.
Prosecutors in most jurisdictions have really good conviction rates. Like 90%+ rates. The feds get something like 99% convictions when they actually go to trial. There's a reason for that: they like slam dunks. They like to bury the opposition. All of these terrible, tragic cases are set up to bury the prosecution instead.