Wait, was I drunk a few months ago when I thought that dude got sent to the slammer?
Actually, if Compean and Ramos had just managed to walk over an aprehend the guy after they crippled him, they could have put in away on charges with the drugs in his car.
But of course, that would have required them to admit they shot him, and also would prove he had no gun if they caught him with no gun.
So they let the guy limp away, and then were unable to identify him. Which, as you say, kind of made it hard to prosecute him for anything.