That is why I am confused by SteveS's arguments. In the agreement it clearly lays out the stipulations that must be followed by the one who is being given immunity and truthfulness is paramount. It clearly states if any of those things aren't adhered to the contract will be null and void. It isn't like Austin didn't know what was expected of him and was blindsided by all of this. So that clause is attached for a purpose and with it being included in all immunity agreements it means the agreement can be rescinded if the one given immunity fails to follow through.
This all came about because of Austin's actions or inactions to fulfill his part of the contract. It is no different to me than one agreeing to pay their mortgage on time every month yet fails to follow through. If that happens then of course the bank has recourse to null and void the contract.
I'm not sure what is causing your confusion, but let me use your bank analogy and see if I can help. As with your example, I'll put the bank in the role of the DA and the homeowner in the role of SA.
1 The homeowner pays (or claims to have paid) every payment on time
2 He gets a foreclosure notice from the bank saying, "You have not paid, so we will foreclose"
3 He contacts the bank, who says, "We say you haven't paid, but we aren't going to tell you what payment you missed. Your mortgage says you must pay, and we'll let you know when we file for foreclosure."
In that circumstance, does he have to wait until the foreclosure is actually filed, before responding? Clearly not, but instead he will file suit pronto to force the bank to PROVE that he has breached the contract (in this example, by missing a payment).
In all of that, it does not presuppose that the homeowner can skip payments and still stave off the foreclosure. But the bank's notice is a breach of their contract, and the bank will be forced to PROVE that one or more payments were missed.
Now return to the DA and SA and the case at hand.
No one - especially me - is claiming that SA has the right to fail to perform. If he doesn't do what he said, he has breached the contract and the DA's duty to provide immunity is over. BUT if the DA wants to pull out of the contract at some point with a claim that SA didn't live up to it, then that action by the DA can be legally challenged with a demand to
prove that SA failed to perform.
And we must keep in mind that what the DA claims to be a failure to perform, might not actually rise to that level once a judge takes a look. For example, if SA told a lie or made a mistake on something, but it was not really important, that would almost certainly not be enough to void the deal. Ultimately, it's up to the court (not the DA) to determine if what SA did is enough to void the deal.