I was playing with a friend on a 13w39b server, and I found out that if you have keepInventory set to true, and the person who gets killed holds an item with his/hers mouse, it keeps 'sticking' to the cursor in the death screen, and the person could drop it out of his/hers inventory. It happened only 1 time, and I killed him with a bow. The other times the person could drop stuff but wouldn't keep it.