Blood Spatter Holds a Message for CSIs
By: Don Penven
Youngsville, NC
In the novel and later the motion picture, “The DaVinci Code,” a Harvard symbologist teams up with a French police cryptologist. The gist of the opening storyline is that the symbologist is called to a murder scene at the Louvre Museum since a note containing the name of this fellow was found on a murder victim. As the story progresses, he meets a young woman cryptologist with the French police, who is the granddaughter of the victim. The two are left alone in the crime scene for a few minutes and they find an Ultra Violet light left behind by crime scene investigators.
Using this UV light, they discover a message that glows under the light beam, written in blood on the museum floor. The message was to the granddaughter. Later the two find a second message written on the back of a painting—The Mona Lisa.
The entire storyline was based on the fluorescence of the nearly invisible blood. But the fact is that in reality—blood does not fluoresce! Yes, that’s how Hollywood depicts crime scene investigation on TV and the Silver Screen. And to perpetuate the illusion, because UV light is invisible, they use a blue (visible) light source to simulate UV.
Blood will—on the other hand—luminesce, that is, it actually is emitting light energy when a chemical like Luminol, BlueStar, Hemiscene or Lumiscene is sprayed on it. So much for Hollywood reality!
Blood spatter (often mistakenly called blood splatter) at the crime scene is a very valuable form of physical evidence. And blood stains can tell quite a story about what actually happened at the scene. Of course many crime scenes have visible blood spattered all over floors, walls and even ceilings. This visible blood poses no collection problems, and the CSI will collect samples from pooled blood as well as the spatter resulting from a blood-drenched knife or baseball bat being swung through the air as repeated strikes are inflicted upon the victim.
It is very important that blood evidence be properly documented and crime scene photos should include the following:
1. Medium wide angle shot of the area
2. Close up with a scale and with surrounding objects included
3. Detailed: Close enough to record direction of travel of blood spatters, with a scale included
In many crime scenes, the perpetrator makes an effort to “clean-up the area,” but rarely do they perform a thorough job of it. Blood on carpet or rugs is easily cleaned off the surface with soap and water. But the underside usually has some residue on it, and the blood may have seeped through to the floor under the carpet.
Even mopping up blood from solid surfaces like tile or wood floors may leave traces—invisible to the naked eye. This is where the CSI employs the chemical reagents that produce luminescence mentioned above.
Sometimes the search yields what is suspected to be blood but confirmation is needed. It may be very obvious to the investigator that the material he observes is blood. But he does have the tools to confirm his hunch to a degree. Two reagents are popular means of determining the “probable, presumptive” presence of blood: Phenolphthalein and Leucomalachite Green.
The crime scene offers grim testimony to what transpired in that place. And the viciousness of the attack is easily discerned by the amount and spread of the victim’s blood. Enter the Blood Spatter Analyst (also referred to as Blood Pattern Analysts, (International Association of Blood Pattern Analysts [IABPA]).
The study of how and why blood is strewn about a crime scene is left to a recently developed breed of crime scene investigators—blood spatter analysts. But is this specialty really needed, and if so—why?
The ancient term, “Blood is thicker than water,” is a truism, because, in fact, blood really has a greater density. For want of a better example, fresh blood has the consistency of the Half and Half we use in our coffee.
When blood drips from a wound onto the floor or is flung through the air when it breaks free of a weapon or a bullet passes through the body, the blood’s trajectory and travel are predictable. And the stains that are left behind can paint a vivid picture of the crime in progress. Blood spatters are words from the grave.
Several factors influence how blood travels on a surface or through the air and how it behaves when it strikes a surface. These factors include gravity, friction and surface tension of liquids. When a drop of blood falls free into the air, during its downward travel it begins with a tear drop shape. But with gravity tugging it down while surface tension holds it together and friction from the air surrounding it, the drop turns it into a perfect sphere until it contacts the surface.
The surface tension struggles to keep the sphere in its round shape but momentum and gravity cause the surface tension to release its grip and it spatters onto the surface. If the drop hits the surface at a straight-down 90-degree angle it leaves a round stain. If it strikes the surface at an angle, the stain becomes elongated. Elongated blood stains can be used to determine, within inches, where they originated from.
And this is what blood spatter analysis is all about. In other articles of this series, you will learn how analysts determine where the victim was when struck or shot and where the perpetrator was positioned.
If this article has aroused your curiosity about blood spatter analysis or crime scene investigation in general, you are invited to download a publication that includes a wealth of training material as well as full descriptions and photographs of the equipment and materials used by real-life CSIs and those depicted on TV and in the movies. CLICK HERE for access to the website.
Download a FREE copy of the “Evidence Collection Mission.”
To receive alerts when new articles are posted, Sign Up For E-Mail Alerts Here
Comments