The point of the prisoner's dilemma is how we are prone to cooperate with others even when it's to our advantage to betray the other guy (even when it's a stranger, or someone we don't like too much.)
Partially, because fuck cops. Whether we're arrested by law enforcement or Nazis (or are wolves fighting off a bear), we hate the bastards more than we distrust our fellow heister.
But as I hinted above, our instinct to stay loyal has evolved since long before we walked upright. Think of the prisoner's dilemma as a recurring thing (because it is, even if the exact specific circumstances are not repeated) the tribe stays more coherent, and more survive if we don't leave our fellow dwarves behind (Rock and Stone!). If we left our buddies to die rather than risk ourselves to rescue them, we'd run out of buddies.
So we never take the deal. Besides which, in the US, you can't trust law enforcement anyway. They are legally allowed to lie to you to secure a confession, even a false one. And they will. Shut up and ask for your lawyer.