A recent study published in the journal Physics of Fluids explored the complex fluid dynamics involved in blood backspatter, a common form of evidence in forensic investigations. Neglecting the interaction between blood and muzzle gases could lead to skewed results.
The researchers, from the University of Illinois Chicago and Iowa State University, modeled the behavior of blood drops during secondary atomization, a process in which larger droplets are torn apart by air drag forces, resulting in smaller droplets. They found that smaller droplets were more easily swept up by the firearm’s gases and turned towards the victim.
The researchers also discovered that muzzle gases form a turbulent vortex ring that pushes blood droplets back towards the victim, and some droplets can even land behind the victim, despite initially moving in the opposite direction.
This finding could explain cases where a short-range shooter remains free of bloodstains, such as the infamous case of Phil Spector allegedly murdering Lina Clarkson.
The researchers hope that their findings will be useful for back spatter analysis in future crime scene investigations, and they plan to study brain tissue spatter in similar short-range shooting events to distinguish between suicides and staged homicides.
Source: American Institute of Physics