Blood Spatter Classifications

Suppose a person died from blunt force trauma to the head, and the victim’s blood is found everywhere at the scene of the crime. How do forensic crime scene investigators determine if a blunt object was the cause of the trauma? If so, how do investigators go about studying blood spatter?

The focus of this article is to explain the different classes of blood spatters.

When studying blood spatters, crime scene investigators have a classification system to analyze spatter.

Blood spatter falls into two classes:

• By velocity: This technique of classifying blood spatters looks at the velocity at which the impacting object strikes the blood source such as the victim’s head and the velocity at which the blood leaves the victim’s head when it is struck. This classification system divides spatters into low-, medium-, and high-velocity spatters. These subgroups are indicative of the object and the mechanism that created the spatter.
• By spatter type: This class is further subdivided into three major types:
  
  • Projection spatters–These are spatters that result from bleeding from the arteries, cast-off blood, and coughed up, or exhaled blood.
  • Impact spatters–These are spatters that occur with gunshots, beatings, stabbings, or any other circumstances where an animate object strikes the victim.
  • Combination spatters: These are spatters that involve a combination of both projection and impact spatters. These are the kind of spatters that are found at many crime scenes. A victim who gets stabbed in the neck or chest may leave behind a combination of both kinds of spatters due to the force of the attack and blood spurts from arterial bleeding, coughed up blood, and cast-off blood.

It is up to forensic crime scene investigators to use both techniques of spatter classes because these techniques overlap one another in many instances.

With advances in science, there is a growing demand for crime scene investigators who are adept in analyzing blood spatter.