Basically, if the proseuction engages in hiding key evidence form the defendant, they can get the conviction set aside and possibly tossed out completely:
The Supreme Court began its analysis by noting that deliberately deceiving the trial court and jury by presenting evidence known to be false had been held to be incompatible with the “rudimentary demands of justice” as early as Mooney v. Holohan, 294 U.S. 103 (1935).[3] In Napue, the Court had held that the same result occurs “when the State, although not soliciting false evidence, allows it to go uncorrected when it appears.”[3] In Brady, the Supreme Court had held that, irrespective of the good faith or bad faith of the prosecution, suppression of material, exculpatory evidence required a new trial.[3]
https://en.wikipedia.org/wiki/Giglio_v._United_States
Yeah, they hid this information from Congress while going after Flynn. Sure looks like they hid it deliberately.
I’ve said this for the past four days; Strzok is the Rosetta Stone of this prosecution and the whole rotten mess can be pulled down because of him. If I were one of Flynn’s or Manafort’s lawyers, I would file an immediate motion for discovery against Mueller, demanding all reoords of the Strzok interview of Flynn, all emails the clown sent out, the hiring files for his wife and her appointment to a 225,000 dollar high level SEC job while he was in charge of reviewing the Abedin/Weiner email cache from Hillary before he gave the “all clear” three days before the election.
Andrew Weissman was guilty of this in his prosecution against Arthur Anderson where he failed to provide the defense with evidence he obtained that would have exonerated the people he was prosecuting. Subsequently the convictions were overturned.