The Legal Theory Bookworm recommends Objection: Disgust, Morality, and the Law by Debra Lieberman & Carlton Patrick. Here is a description:
Why do we consider incest wrong, even when it occurs between consenting adults unable to have children? Why are words that gross us out more likely to be deemed "obscene" and denied the protection of the First Amendment? In a world where a gruesome photograph can decisively influence a jury and homosexual behavior is still condemned by some as "unnatural," it is worth asking: is our legal system really governed by the power of reason? Or do we allow a primitive human emotion, disgust, to guide us in our lawmaking?
In Objection, psychologists Debra Lieberman and Carlton Patrick examine disgust and its impact on the legal system to show why the things that we find stomach-turning so often become the things that we render unlawful. Shedding light on the evolutionary and psychological origins of disgust, the authors reveal how ancient human intuitions about what is safe to eat or touch, or who would make an advantageous mate, have become co-opted by moral systems designed to condemn behavior and identify groups of people ripe for marginalization. Over time these moral stances have made their way into legal codes, and disgust has thereby served as the impetus for laws against behaviors almost universally held to be "disgusting" (corpse desecration, bestiality) - and as the implicit justification for more controversial prohibitions (homosexuality, use of pornography). Written with a critical eye on current events, Lieberman and Patrick build a case for a more reasoned approach to lawmaking in a system that often confuses "gross" with "wrong."
And from the reviews:
"Debra Lieberman and Carlton Patrick have eloquently exposed a rather unreliable bug in human nature: a tendency we have to equate disgust with moral disapproval. Just because something is yucky to us, we tend to jump to the conclusion that it is morally wrong. This is a dangerous basis for law making, and evolutionary psychology can help to explain our own irrationality to us." -- Matt Ridley, author of The Red Queen and The Evolution of Everything
"Objection is a fascinating investigation of the complex relationship between the psychology of disgust and the legal process. Lieberman and Patrick's vivacious and original analysis shows why ancient moral intuitions are a bad basis for making judicial decisions. This elegant integration of evolutionary psychology and legal theory would be important at any time. It is all the more valuable now when divisive politics are increasingly jeopardizing legal protections for the vilified and powerless." -- Richard Wrangham, Ruth B. Moore Professor of Biological Anthropology, Department of Human Evolutionary Biology, Harvard University, and author of Demonic Males and Catching Fire
"Objection is fascinating in so many ways. It explains an intriguing and far from-obvious discovery about our emotional makeup. It explores the conceptual relationships among issues in psychology, morality, and jurisprudence with precision and clarity. And it is enlivened with unforgettable cultural practices, legal cases, and scientific discoveries. This book will stand as a landmark in how to apply our growing knowledge about human nature to issues in the law." -- Steven Pinker, Johnstone Professor of Psychology, Harvard University, and author of How the Mind Works and Enlightenment Now
"Ever wonder why some people feel disgusted and why disgust matters? When people think something is gross, they think it must be wrong. Disgust plays an important role in regulating sex, morality, pornography and myriad matters in the legal world. Nowhere has this case been made more convincingly than in Lieberman and Patrick's terrific book, Objection."-- Elizabeth Loftus, Distinguished Professor of Social Ecology, and Professor of Law and Cognitive Science, University of California, Irvine