A friend of mine, who I will not name, used to get pulled over a lot, for a variety of reasons (often deserved).
This happened often enough, and his lawyer always advised him to not say a word, but especially when he'd been drinking, the act of getting him to talk long enough to say that he was invoking his right to silence would usually reveal that he'd been drinking.
To mitigate it, he printed a laminate card, that he kept in his wallet, which very respectfully and politely invoked his right to silence. When pulled over, he would simply remove the card from his wallet and hand it to the officer.
I don't know that it ever got him into or out of any trouble, but at least he had a routine, and it prevented him from talking unnecessarily.
Perhaps the author could have made use of something like this?
If I'm being perfectly honest, it wouldn't have surprised anyone if at any time he had to spend the rest of his life in jail. He's not someone I was ever particularly proud of knowing, and in fact, the only impressive thing about him, ever, was that he carried that card around.