ISSN: 0022-1198
CODEN: JFSCA
Published Online: 1 January 2005
Page Count: 10

Deducing Drop Size and Impact Velocity from Circular Bloodstains
Hulse-Smith, L
Princess Margaret Hospital, Ontario

Mehdizadeh, NZ
University of Toronto, Ontario

Chandra, S
University of Toronto, Ontario

(Received 28 June 2003; accepted 2 September 2004)

Abstract

An experimental study was done to determine the diameter and velocity of blood drops falling on a surface by measuring the size of bloodstains they produced and counting the number of radial spines projecting from them. Bloodstains were formed by releasing drops of pig blood with a range of diameters (3.0–4.3 mm) and impact velocities (2.4–4.9 m/s), onto four different flat surfaces (glass, steel, plastic, paper) with varying roughness (0.03–2.9 µm). High-speed photography was used to record drop impact dynamics. Bloodstain diameters and the number of spines formed around the rim of stains increased with impact velocity and drop diameter. Increasing surface roughness reduced stain diameter and promoted merging of spines, diminishing their number. Equations are presented that explicitly relate drop diameter and impact velocity to measurements of stain diameter and number of spines.

Keywords:
forensic science, bloodstain pattern analysis, blood drop, pig blood, drop splashing

Paper ID: JFS2003224
DOI: 10.1520/JFS2003224
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