The S.P.E.A.R. System is grounded in the "flinch response" of the person subjected to a sudden, surprise physical assault. The flinch response is an involuntary physiological response to an unexpected attack that is highly consistent and functions as an effective protective mechanism. Flinching is the lightning-fast, whole-body, instinctive protective response to an assault. The S.P.E.A.R. System is based on converting various identified types of flinch responses into effective defensive responses. By training officers in ways that allow them to accept and use the flinch, they are better able to survive any close-quarters ambush. This article explains the scientific, biological facts of the flinch response which involves an analysis of how the brain operates to prepare the body to protect itself when under attack. Learning to convert the body's natural flinch response will improve officer survivability when combined with any current defensive tactics program. Every defensive tactics instructor should attend S.P.E.A.R. School.