Where Does Advocacy End and Obstruction Begin?

‘Even in the very few instances where the accused has intrusted his defender with a full confession of his crime, we hold it to be clear that he may still be lawfully defended. The guilt of which he may be conscious, and which he may have so disclosed, he has still a right to see distinctly proved upon him by legal evidence … Human beings are never to be run down like beasts of prey, without respect to the laws of the chase.’