Commentary: Approaching and stalking public figures--a prerequisite to attack.

The concept of studying approaches to public figures (i.e., physical pursuit or stalking) arose as a proxy measure to aid in the development of tools to prevent assassination, a low base rate event. In this commentary, we review the origins of this concept and the historical record of public figure attacks in the United States that formed the empirical basis of the concept, we describe case examples of approaches toward public figures in the United States that did not result in injurious attacks, and we provide a synopsis of our findings on the ways in which communications predict approach.