"Look, the only reason to kill a guy you're extorting, logically, is if he's ratted you out to the cops. Which he sort of did. But apart from us, and Joe himself, the only other person who KNEW Salt is working with the cops and that he talked to Joe are the cops. And who would possibly turn down help escaping the cops, apart from someone who has a legitimate reason to be at the crime scene the cops are currently heading to? A cop, for example. 'Oh, I was taking a stroll and heard gunshots, so I came running and this guy pulled a gun on me so I shot him'."
I pull out the ledger.
"And it's fairly obvious that only one of them is a decent criminal. One went a long with a plan which boils down to 'get arrested', and the other gave a puppet maker his name and address. But not his phone number, which is the only reason I found it suspicious."