The procedures vary somewhat from state to state, but generally a prosecutor can charge with an "Information" (Which is I believe what this 'Probable cause affidavit' is in more-traditional terms) or by presenting a highly-selective 'best-case' version of it, without any defense evidence to contradict it or anything being presented about affirmative defenses like self-defense, to a grand jury, which produces an "Indictment" or "Returns a true bill," if they think the prosecutor has at least some credible evidence on all the elements of the offenses brought before it (Hence the saying, 'You can indict a ham sandwich').
IOW, they ain't gonna be no indictment.
Okay. If I'm getting this right, whatever document the prosecutor/district attorney prepared goes to a grand jury. Grand jury does what it does and if they deem the charges are credible, it then goes to trial.
I know nothing about the legal profession, but I believe the burden of proof on the prosecution with grand juries is a whole lot less of a requirement meaning it doesn't take much to return a "Yep, you've got something here, Mr. DA".
Is that about right, DAT?