Any scientific psychologist who has interacted extensively with police, lawyers, or trial judges has learned that scientific psychology and the legal system are very different beasts. The differences run much deeper than mere language and instead represent different types of thinking-a clash of cultures. This clash is particularly apparent when psychologists attempt to use research findings to affect legal policies and practices. In order for scientific psychologists to work effectively in applying psychological science to the legal system, they will need to develop a better understanding of the concept of policy and the contingencies that exist for policymakers.