I've read this whole article and I still don't understand why the ammo is important?
Yeah, it is bad that the prosecution did not disclose it, but it was a manilla envelope of loose rounds handed over by a friend of the father of the armourer, who has already been convicted of manslaughter. I can see why they would deem it not to be relevant evidence.
How could it possibly help the defence (other than this exact situation where it got the case thrown out)?
Also why would it not just be a mistrial, rather than the case being thrown out to never be tried again?
If Baldwin provided all the ammo used, it increases the likelihood he is convicted by a jury. This ammo would've been provided to the Armorer by a third party, without his knowledge. At trial, the defense could have made any number of arguments that Baldwin had no way of knowing live ammunition was on set because an outside individual brought it to the set.
In any case, it's a clear Brady violation. The prosecutor has a constitutional duty to provide exculpatory evidence to the defense. It's not up to them to decide if it will be enough to establish reasonable doubt.
What the prosecution did was place this evidence under a new, case & number for a non-existent crime. They never had any intention of investigating the case that ammo was assigned to. The only reasonable conclusion one can draw was the prosecution deliberately obfuscated the relationship that ammo had to Baldwin's case to avoid providing it.
In an already highly attenuated case, and with overwhelming evidence that Baldwin's rights were violated, there can be no fair trial going forward. From the perspective of the law, once the prosecution has been found to have violated Brady deliberately, there can never be due process for the defendant.
I don't think she planned on getting caught. This was a once in a lifetime case for her. Securing a conviction would elevate her career substantially. It's not unprecedented for prosecutors to engage in this kind of misconduct.
That said, most Brady violations are from incompetence rather than malice. Tons of evidence--not just exculpatory--has been lost by poorly trained or lazy investigators.