Well, I did something useful for once; I leveraged the power of statistics to figure out how to spot characters who have only one working eye and are trying to hide it. Using Kansuke as my model and Koumei and Conan as controls, I was able to preliminarily identify the traits of one-eyed characters by simply counting the number of panels where they turn their heads and look a certain way. I then applied the results to Rumi, Kuroda, and Sakurako Yonehara. Kuroda has too few points to go off of, but an interesting lack of head turning. Rumi appears to have two working eyes, but there is not enough data to tell for sure. Sakurako was much more definitive: two working eyes and an honest disposition that avoids sideyeing characters. Mathematically, Sakurako is out of the running for Rum. From now on, any new character who appears for 2-3+ cases will not be able to hide from the powers of math.
You can see the results and more Rum hunting tips here: http://www.detectiveconanworld.com/wiki/User:Chekhov_MacGuffin/Vision