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Prediction of blood back spatter from a gunshot in bloodstain pattern analysis

P. M. Comiskey1, A. L. Yarin1,*, S. Kim2, and D. Attinger2

  • 1Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, 842 W Taylor Street, Chicago, Illinois 60607-7022, USA
  • 2Department of Mechanical Engineering, Iowa State University, 2529 Union Drive, Ames, Iowa 60011-1210, USA

  • *Corresponding author: ayarin@uic.edu
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Phys. Rev. Fluids 1, 043201 – Published 2 August, 2016

DOI: https://doi.org/10.1103/PhysRevFluids.1.043201

Abstract

A theoretical model for predicting and interpreting blood-spatter patterns resulting from a gunshot wound is proposed. The physical process generating a backward spatter of blood is linked to the Rayleigh-Taylor instability of blood accelerated toward the surrounding air, allowing the determination of the initial distribution of drop sizes and velocities. Then the motion of many drops in air is considered with governing equations accounting for gravity and air drag. Based on these equations, a numerical solution is obtained. It predicts the atomization process, the trajectories of the back-spatter drops of blood from the wound to the ground, the impact angle, and the impact Weber number on the ground, as well as the distribution and location of bloodstains and their shape and sizes. A parametric study is undertaken to predict patterns of backward blood spatter under realistic conditions corresponding to the experiments conducted in the present work. The results of the model are compared to the experimental data on back spatter generated by a gunshot impacting a blood-impregnated sponge.

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Synopsis

Recreating the Scene of a Crime

Published 2 August, 2016

A new theory accurately predicts the speed, sizes, and trajectories of blood drops resulting from gunshot wounds.

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Phys. Rev. Fluids 1, 043201– Published 2 August, 2016
  • Received 16 March 2016

©2016 American Physical Society

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