The use of computed tomography (CT) scanning in blunt head trauma has increased dramatically in recent years without an accompanying rise in the prevalence of injury or hospital admission for serious, traumatic conditions. Because CT is neither harmless nor inexpensive, researchers have attempted to optimize utilization, largely through research that elucidates which historical elements, signs, and symptoms predict intracranial injury, and use this information to develop clinical decision instruments (CDIs). While such techniques may be useful when the benefits and harms of each strategy (neuroimaging vs. observation) are known, quantifiable, and amenable to comparison, the exact magnitude of these benefits and harms remains unknown in this clinical scenario. We believe that most CDI development efforts are misguided insofar as they ignore critical, non-clinical factors influencing the decision to image. In this paper, we propose a conceptual model to illustrate how clinical- and nonclinical-factors influence emergency physicians who are making this decision. We posit that elements unrelated to standard clinical factors, such as personality of the physician, fear of litigation and of missed diagnoses, and compensation method may have equal or greater impact on actual decision-making than traditional clinical factors. Further, we suggest that the paucity of research on nonclinical factors is not surprising as such research requires expertise not typically possessed by emergency medicine clinician-researchers. Acknowledgement and study of these factors will be essential if we are to understand how EPs actually make these decisions and how test-ordering behavior can be modified.