Pre-trial Hearings
When a prosecuter brings a serious charge (as opposed to a grand jury indictment) the system says, "The first step is to see whether there's anything here."
Does the prosecuter have a good reason for the charge? You want to know that before subjecting everyone to a full trial.
So there will be a hearing where the prosecution puts forward enough evidence to show a reason for the charge. When there is obviously enough evidence for the charge to be plausible the defense will usually do nothing because it can only hurt.
The defense is able to keep their defense strategy under-wraps, so if the case is likely to go to trial either way, why give anything away in a forum that is unlikely to get you freed?
An irony arises, however. In a closely followed case, particularly if hearings are televised, the public gets persuasive evidence of guilt up front, and no defense for months. So the process firms up public perception of slam-dunk guilt well before the trial.
This is a general observation. It is inspired by the fact that there will be pre-trial hearings in the Zimmerman case but it is not about the Zimerman case.
Now, in the Zimmerman case there is a specific and unusual pre-trial wrinkle. The defense can mount a legal claim of sef defense that will be weighed by the judge rather than a jury. For that reason the pre-trial hearings in this case mey be more two-sided than usual.