The fascination with forensic science has surged in recent years, fueled by an increasing interest in “true crime” content. Many are now familiar with the concept that evidence from a crime scene, like blood, can disclose crucial details to aid in the investigation and understanding of a crime. Scientific techniques play a vital role in decoding this evidence.

In a recent publication in Physics of Fluids by AIP Publishing, a team of researchers from Boston University and the University of Utah explored how bloodstains can provide more intricate details than what is traditionally extracted by forensic experts.

The study focused on the small protrusions extending from the main elliptical shape of bloodstains, known as “tails.” According to James Bird, one of the authors, these tails are usually referenced only to determine the direction of the blood droplet’s travel but are often overlooked for further analysis.

Prior research has mainly concentrated on large blood droplets falling on flat or inclined surfaces, where gravity plays a significant role in altering and masking these tails.

This new research, however, conducted high-speed experiments with small human blood droplets, less than a millimeter in diameter, impacting horizontal surfaces at different angles. Bird noted that the process creating the tail length is distinct from the one that forms the size and shape of the bloodstain’s elliptical part. This means the tail length contains separate information that can assist in pinpointing the blood drop’s original location.

The study reveals that tail length can indicate the size, speed, and angle of impact of the blood drop that created the stain. When multiple blood stains in a pattern are analyzed, their trajectories can be traced back to their source.

Although the research currently focuses on impacts on horizontal surfaces, Bird and his team hope this encourages further studies on tail lengths in bloodstain patterns, enhancing standard bloodstain analysis with more comprehensive data.

Understanding the origin of bloodstains at a crime scene can significantly aid detectives. It can help determine the position of a victim during an incident or support or challenge witness statements, as Bird suggests.

Story Source:

Materials provided by American Institute of Physics. Note: Content has been edited. 

Journal Reference:

1. Garam Lee, Daniel Attinger, Kenneth F. Martin, Samira Shiri, James C. Bird. Bloodstain tails: Asymmetry aids reconstruction of oblique impact. Physics of Fluids, 2023; 35 (11) DOI: 10.1063/5.0170124