Influence of the impact energy on the pattern of blood drip stains

Abstract

The maximum spreading diameter of complex fluid droplets has been extensively studied and explained by numerous physical models. This research focuses therefore on a different aspect, the bulging outer rim observed after evaporation on the final dried pattern of blood droplets. A correlation is found between the inner diameter, the maximum outer diameter, and the impact speed. This shows how the drying mechanism of a blood drip stain is influenced by the impact energy, which induces a larger spreading diameter and thus a different redistribution of red blood cells inside the droplet. An empirical relation is established between the final dried pattern of a passive bloodstain and its impact speed, yielding a possible forensic application. Indeed, being able to relate accurately the energy of the drop with its final pattern would give a clue to investigators, as currently no such simple and accurate tool exists.

Using the likelihood ratio in bloodstain pattern analysis

“…It describes how a bullet atomizes blood; how the impact of a fist on a moving face squeezes and splashes blood; how airborne droplets move along trajectories curved by gravity and slowed by drag; and how drops spread, wick, and dry onto materials as complex as fabrics. Only recently, peer-reviewed fluid dynamic studies have started to uncover the complex physics underlying BPA [54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69][70][71][72]. The governing equations of fluid dynamics are called the Navier-Stokes equations; they are the expression of Newton's second law for fluids.…”

Droplet impact of blood and blood simulants on a solid surface: Effect of the deformability of red blood cells and the elasticity of plasma

“…Brutin et al have demonstrated that red blood cells will affect the dried bloodstain pattern [39]. Besides, Smith et al found a correlation between dried bloodstain pattern and droplet impact energy [40]. These studies indicate that particles that simulate red blood cells need to be added to the BS used for bloodstain pattern analysis.…”

Transient Prediction of Nanoparticle-Laden Droplet Drying Patterns through Dynamic Mode Decomposition

“…The DOD process was modeled and analyzed via the drying of droplets. , Until now, DOD studies were investigated concerning the geometric properties of the droplet (volume, diameter, etc. ), viscosity, surface tension, density, and surface energy and roughness. − Also, the impacts of pH and surfactant on the drying pattern were analyzed by using the various droplet and substrate characteristics. − Another example is the blood/surrogate blood droplet evaporation in biological applications with the assumption of the blood droplets as the suspension-laden ones that were modeled with respect to the humidity effect, crack formation, , surface roughness and wettability, relation between the number of cracks and droplet diameter, evaporation rate, and impact energy . Besides the aforementioned cases, we have been working with droplet evaporation with nanoparticle-laden droplets by investigating the flow regime and deposition patterns of binary mixtures, , disk-to-dual ring deposition, , and impacts of (i) surfactants on the droplet deposition and (ii) multisized nanoparticles .…”