Phrenology
A hundred years ago, popular theories claimed that you could distinguish a criminal by the shape of the skull. Those theories were largely wrong, but nevertheless we are finally starting to admit [again] that moral IQ has some genetic connection. I've never understood why otherwise sensible people can acknowledge the innateness of, say, math and music abilities, while violently denying that moral ability is also partly innate. (Actually I do understand; leftist orthodoxy requires us to believe that everyone is equally redeemable if given the appropriate environment.)
These three women form an interesting case study. Left is the Belgian suicide bomber, Muriel DeGauque. Center is the Jordan hotel suicider (unsuccessful) Sajida al-Rishawi. Right is, of course, Squeaky Fromme. All three followed a murderous cult to its extreme conclusion. Their skulls may not be similar, but their faces show a kinship of emotion and soul.