When blood hits clothes, physics takes over
The creation of simulated evidence on crime locations can help forensic doctors better read the stories left by horrible blood stains. To decode some of these bloody stories, a whole team from the North Carolina State University needed was a combination of high -speed cameras, cotton fabrics and a little pork blood. Their conclusions on how common clothes react to blood are detailed in the September 2025 issue of the journal Forensic International Science,,
Legal science is a relatively new concept, historically speaking. There are several major moments in its development, but the field of studies can be widely traced 115 years ago to a man named Edmond Locard. In 1910, the French criminologist first proposed his theory according to which “each contact leaves a trace”, a concept now known as the Locard exchange principle. These traces appear in many forms – including blood spots. But as the principle of Locard indicates, the traces are also influenced by the conditions of contact itself.
More than a century later, there are many high -tech methods to analyze the blood stains of a violent crime scene. The forensic doctors bring together evidence to the molecular level, but even a close visual reading of the situation often offers invaluable information. For example, blood spots can indicate the type of weapon, the angle of attack and the impact force. However, these models are frequently influenced by the interaction of the surface material with the blood itself, especially when this material is cotton clothes. According to researchers from the North Carolina State University, the results can be frustrating.
“Textiles have complicated structures and are often absorbent. These characteristics can lead to highly distorted forms of blood pillowcases, “wrote the team in their study, adding that” the complex characteristics of stains can make the analysis of models of blood spots more difficult and less simple. “
“When blood strikes the fabric, it leaves a stain. But it can be difficult to assess things like the speed with which the blood was deployed when it hit the fabric,” said a Tiegang Fang, one of the corresponding authors of the study and a mechanical and aerospace teacher of the state of NC. “Did it happen quickly? Has anyone simply brushed blood? It is difficult to say, because once the blood came into contact with the fabric, it crosses the surface of the fibers in the fabric, spreading.”
This process frequently creates thin spins called “fingers” which extend from a Bloodstain center, further complicating analysis. To study these attributes and others, Fang and her colleagues used pork blood treated to behave in a coherent way through the tests. They then aligned five cotton fabrics – cotton woven plain, the front and back of the cotton headband, as well as the front and back of a jersey knit. Then, the team used several high -speed cameras to capture the four -frame fabrics per second, splashing the textile samples at 12 different speeds. They reviewed the images of their damage and quickly noticed the particular behavior of the fingers of each stain.
“We found that the more fingers there were, the more a blood stain has, the more the blood moved quickly when it hit the fabric,” said Fang. “However, over time, these fingers can spread and run together.”
Another major speed indicator came from what is called satellite droplets. These are created when rapid blood strikes the fabric, creating secondary spots around the central brand.
“The more the blood moved quickly, the more satellite droplets,” added Fang.
Some cotton weaving, however, told a story than others. The physical properties of cotton woven in simple were much easier to read, while the sowing turned out to be more difficult.
“It is clear that the specific structures of each surface play an essential role in the way these blood spots are formed and what we can learn,” concluded Fang.
Researchers hope to conduct similar experiences on a wider range of fabrics, wires and weaving. A better understanding of the interactions between these variables and others could help build a knowledge base which can then be applied to the scenes of forensic crime.
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