ARTICLE Original Article Estimating Occult Timing of Surprise Gunshot Sounds in Silent Film via Observed Start of Human Voluntary Reactions of Concern Brian Roselle1 & Kenneth Scearce2 1Fairfield, OH, USA 2San Francisco, CA, USA ABSTRACT ARTICLE INFORMATION Voluntary human reactions, and associated perception times when reaction movements commence, are iden- Received: 2 March 2019 tified to estimate gunshot sound arrival time to subjects in a shooting scenario recorded on silent film. Com- Revised: 23 January 2020 mon involuntary reactions (startle) and voluntary reactions are reviewed to help identify proper reaction Accepted: 29 January 2020 types being observed and apply in back-calculating gunshot timing. With a focus on voluntary reactions, Published: 8 August 2020 values for perception time as a function of stimulus expectancy, specifically in the case of a surprise stimulus, Citation: Roselle B, Scearce K. Estimat- are determined by reapplication of brake perception-reaction time (brake PRT) modeling of extensive driver ing Occult Timing of Surprise Gunshot Sounds in Silent Film via Observed reaction time studies in traffic flow theory. Using a modified model in conjunction with sampling human Start of Human Voluntary Reactions reactions observed on film allows back-calculating surprise gunshot sound timing. To detail use of this of Concern. J Assoc Crime Scene approach, a well-known example of a silent film, the Abraham Zapruder film of the Kennedy shooting, is Reconstr. 2020;24:1-22. considered to help identify the first shot timing in that case. Author contact: Keywords: chronology, gunshot timing, perception-reaction time, perception time, surprise voluntary
[email protected] reaction, startle reaction, Zapruder film, shooting reconstruction, crime scene reconstruction, forensic science
[email protected] Introduction An integral part of overall crime scene throughout the scene and are often critical to reconstruction is determining the chronological the overall analysis”.