This discussion recently came up on emacs.stackexchange.. http://emacs.stackexchange.com/a/21524/115

The emacs manual (C-h i g (emacs) Modifier Keys) says the below:

"A <Control>-modified alphabetical character is always considered
case-insensitive: Emacs always treats ‘C-A’ as ‘C-a’, ‘C-B’ as ‘C-b’,
and so forth. The reason for this is historical."

But I am able to bind something like

(global-set-key (kbd "C-S-n") #'previous-line)

and have C-n and "C-N" call different commands.