Do they really presume him innocent?
Of course not.

They presume him guilty.

"So soon as I see him come through dot leetle door in the back of the room, then I know he's guilty!" as the foreman said in the old story.

What good does the presumption of innocence, so called, do for the miserable Robinson?
None whatever--save perhaps to console him in the long days pending his trial.

But such a legal hypocrisy could never have deceived anybody.