When a violent crime occurs, there's always a high likelihood of bloodshed. Investigators conduct bloodstain pattern analysis (BPA) when solving such crimes. BPA is the analysis and interpretation of bloodstains at a crime scene to determine where the crime occurred, the perpetrator's actions, and witness statements' accuracy. This piece is an overview of how BPA is conducted and the type of bloodstain patterns at a crime scene.
How is BPA Conducted?
Investigators conduct BPA in two phases; pattern analysis and reconstruction phases. Pattern entails forensic analysis of the physical characteristics of blood at the crime scene. That includes shape, size, surface texture, and distribution of the patterns. This phase answers questions like where the blood came from, the nature of the crime, the movement of the offender and the victim, and the directions from which the offender attacked the victim.
The reconstruction phase entails scientific analysis of the bloodstains to determine the type of crime, whether the blood was from the victim or the offender, and if a suspect's DNA is at the crime scene. Forensic experts use scientific and mathematical principles to determine the point of convergence, i.e., where the bloodshed emanated from and the type of weapon used by the perpetrator leading to the nature of bloodstains.
Types of Bloodstain Patterns
During BPA, investigators classify bloodstains into the following categories.
1. Passive Patterns
Passive bloodstain patterns refer to the force by which blood lands on the ground. It is majorly due to the effect of gravity on the blood. During BPA, the analysts examine the drip stains and blood pool to determine the nature of the passive patterns. Drip stains occur when blood drops without an alteration or disturbance, resulting in a single-shaped pattern instead of smaller droplets. Passive patterns can result from blood dripping from a person being hit with a blunt weapon or due to trauma injuries.
2. Spatter Patterns
Spatter patterns occur when the victims are struck by hard solid objects or shot. Spatter patterns can either be back or front spatters. Back spatter patterns form when bloodshed is from a hard body surface, e.g., a bullet hitting the skull, making blood drip in the opposite direction from the point of impact. On the other hand, front spatters are blood patterns formed from blood dripping toward the same direction as the point of impact.
3. Altered Patterns
This occurs when physical activity has occurred after the crime and changes the original 9blood patterns. For example, an altered pattern can result from dragging the body over a pool of blood or footprints on the bloodstains. Altered patterns help investigators know the activities that took place during the crime and the objects used by the offender.
Final Word
BPA is an important part of criminal investigations and the collection of evidence. If you find yourself at a crime scene where bloodshed has occurred, do not alter the bloodstains, i.e., stepping into the blood or touching the bloodstains. That may affect the chances of solving the crime. Instead, contact bloodstain pattern analysis services to assess the scene.
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