The Romantics used to say that the eyes were the windows of the Soul. A good Alien Xenologist might not put it quite so poetically. but he can, if he's sharp, read a lot in the look of an eye!
It's hard to ferret out a gang of fanatics; it would, obviously, be even harder to spot a genetic line of dedicated men. But the problem Orne had was one step tougher than that!