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?