Let's imagine for a moment - that I am a special prosecutor - have an evil doer (for these purposes we will refer to him as Official "A") - by the short ones - on charges of lying to investigators, perjury, and obstruction of justice - all very serious crimes - with someone going to jail - it is not me.
Naturally, Official "A" is an unhappy person - very unhappy - all the money in the world - his good looks - powerful friends - high priced defense lawyers - can't help him beat this rap.
Also imagine - there might be other evil doers on my radar - Official "A-" and Official "A+" - that this special prosecutor - is building cases against as well.
In exchange - for Official "A's" cooperation and testimony - in helping bring these other evil doers to justice - hypothetically - I just might cut Official "A" some slack - on one or more charges - at sentencing.
[More than 90 percent of federal defendants plead guilty. Some do so during the pretrial phase as part of a plea bargain, in exchange for the prosecutors' dropping some charges or recommending a more lenient sentence.]
Naturally - as a special prosecutor (remember, humor me) - I have presented evidence - before a grand jury - on more than one occasion - finding of probable cause for grand juries - necessary to issue an indictment – is a relatively low standard of proof.
Finally - imagine - 12 of the 23 jurors - have already voted to indict Official "A" - consider the proposition - that I might want to keep that information secret (e.g. "sealed") - use it as leverage - to negotiate with Official "A" - and his lawyer - for unconditional cooperation - to bring all the evil doers to justice.
In a perfect world - this would be - swell.
Happy Friday - have a great weekend. :D