To be the devil's advocate - gathering evidence IS the attempt of proving guilt.
That makes no sense. You can't break-into someone's house to gather evidence just because you feel like it. There are rules that must be followed, and yes, the law applies to the govt. too. Even if they have the means to skirt the law via warrants, etc, they must follow procedure. TBH, I'm glad the judicial branch is starting to get a backbone.
Mathematics is the only science where one never knows what one is talking about nor whether what is said is true. -- Russell