Investigating Bloodstain Patterns: Techniques and Analysis

Summary

In this article, we explore the techniques used by forensics experts to investigate bloodstain patterns. We discuss the importance of safety and avoiding contamination at a crime scene, as well as the three main categories of bloodstains. We also delve into the various types of bloodstain patterns that can be found at a crime scene and how they can be analyzed to determine the origin of the blood.

Passive, Transfer, and Projected Bloodstains
Types of Bloodstain Patterns
Analyzing Bloodstain Patterns

Passive, Transfer, and Projected Bloodstains

Forensic experts categorize bloodstains into three main categories: passive, transfer, and projected. Passive bloodstains are created by the force of gravity and include drips, flows, and pools. Transfer bloodstains occur when a surface with blood comes into contact with another surface, leaving a pattern on the second surface. Projected bloodstains are created by a force other than gravity and include spatters, splatters, and arterial spurts.

Types of Bloodstain Patterns

There are various types of bloodstain patterns that can provide valuable evidence at a crime scene. Satellite stains are forced out from the center of a main stain due to disruption. Contact transfer stains occur when a bloody surface comes in contact with another surface, and can provide valuable evidence about the suspect. Shoe wear impressions and transfer patterns in textiles can also provide important evidence. Movement can affect transfer stain patterns, causing a feathering effect. Flow patterns are caused by gravity and can provide information about the victim’s injuries and position at the time of the injury. Saturation and pooling patterns can indicate where a victim was bleeding for a period of time. It is important to document and analyze all types of bloodstain patterns at a crime scene.

Analyzing Bloodstain Patterns

Bubbles in a blood stain could indicate an expired or airway pattern, and an accumulation of blood on a non-porous surface could lead to pooling and saturation. Impact spatter is another type of bloodstain pattern that results from an external force on an open source of blood. Bludgeoning is the most common cause of these stains, but they can also result from a bullet passing through someone’s body. To determine the origin of the blood stains, forensic experts calculate the area of convergence. They use the long axis of several stains to draw lines that converge in the center of the area, and use arrows to show the direction of the stains.

Conclusion

Bloodstain pattern analysis is a critical component of forensic investigations. By categorizing bloodstains and analyzing their patterns, forensic experts can provide valuable evidence about what happened at a crime scene. It is important to approach a crime scene with caution and avoid contamination to ensure the accuracy of the analysis.