It seems like hardly a week goes by these days that we do not here of someone being killed by blunt force trauma. A young woman hiker in Georgia disappears on a hike through a state park near Atlanta. Her body is eventually found and the medical examiner determines that her death was due to blunt force trauma to the head; the body was also decapitated. Just this month a twenty year old pregnant female marine Lance Corporal stationed at Camp Lejeune, North Carolina is found dead the victim of blunt force trauma to the head by a weapon probably a crow bar or tire iron.
What is blunt force trauma?
Blunt force trauma is kind of an umbrella term. It is non-specific but sufficient enough to put on a death certificate. However, it can take many forms. Blunt force trauma is caused by a blunt object striking some part of the body. The blunt object may be a bat, wrench, hammer, floor, dashboard, etc. The typical signs of blunt force trauma include lacerated major blood vessels or aorta, lacerated or crushed organs, hematoma, crushed or severed spinal cord or fractures of the skull. Any one of these injuries is sufficient to cause death.
While automobile accidents and accidental falls represent the greatest causes of blunt force trauma, this type of injury is also present in a wide variety of homicide cases when gunshot wound is not the cause of death. Most homicides involving blunt force trauma result from the victim being struck in the head or neck with an object such as a hammer, fireplace poker, flower vase, etc. In these cases the bones of the skull or neck are fractured in one or more places by the velocity of the blow. Blunt force trauma can also occur if the victim has been severely beaten with an object or with fists. In these cases the injuries are generally to internal organs like the kidneys, liver, spleen, etc.
Blunt Force Trauma to the Brain
The brain can be damaged by trauma in two ways. When the head is struck by a hard object the cerebral cortex (gray matter) can become bruised. If the force of the blow is sufficient to cause a whiplash like circumstance then the injury can occur to the nerve cells (axonal injury) deep in the white matter of the brain. Injury of this type involves a variety of forces including the acceleration of the object and the acceleration force imparted to the brain by the object. Injury results from the direct contact between the object and the head and the greatest injury to the head occurs from the initial direct impact with the blunt object. The area of contact may be large (a baseball bat, 2x4) or small (hammer head, a paper weight) but the velocity of the impact will largely determine the extent and type of damage caused by the resulting blow.
The cranium, the complex structure of bones that encloses and protects the brain, is composed of three layers; the outer table (hard outer layer of bone), the inner table (inner layer of hard bone), and the diploe or spongy bone layer between the two.
When the blunt object comes into contact with the bones of the human skull several reactions are possible. A piece of bone may break loose from the skull and be forced into the cranium with concentric fractures forming around the break area. This bone fragment or plug as it is called often takes on the approximate shape of the object itself. Another reaction is where the object causes an inward bending of the skull resulting in crushing of the outer table and diploe with fractures radiating outwards. In this case the inner table is left untouched by the blow. A blow can also cause a situation where there is both inward and outward bending of the skull structures. In this case, the inner table as well as the outer table and diploe are all shattered. Radiating fractures spread outward from the impact site.
Weapons Characteristics
The number and type of objects that can potentially be used in a crime to inflict blunt force trauma on a victim is almost immeasurable. However, it is possible to identify certain characteristics of the resulting wound which allow a group of potential weapons to be identified. This is called a "class characteristic". A fracture showing smooth curved lines would be caused by a similar class of weapons such as a claw hammer or crow bar. Some times a weapon will leave individual marks on the bone. These marks might arise from imperfection in the manufacture of the object or marked caused by prior damage to the blunt object itself. Such marks are referred to as "individual characteristics" and can further serve to identify a particular object as the murder weapon.
Sometimes a single weapon can produce more than one type of fracture wound. For example, if the victim was hit with the flat side of a shovel blade then a large flat area of one or more fractures would be evident on the head. However, if the victim was hit with the shovel blade turned on its side the resulting wound would be a linear fracture possibly exhibiting a pattern with curvature similar to that of the shovel blade. In many cases a victim will display several occurrence of blunt force trauma. It is the job of the medical examiner and forensic investigator to determine if all the wounds were made by the same object and to try to determine which wound occurred first,
Blood Spatter in Blunt Force Trauma
As in most crime scenes blood spatter pattern analysis can provide vital evidence in determining what actually happened during the commission of the crime. Blunt trauma to most of the body may not produce significant blood spatter since most of the blunt force damage will be to internal organs. Blunt trauma to the head and neck, on the other hand, almost always results in a series of characteristic blood spatter patterns. The blood spatter is characteristic of medium velocity blood spatter resulting from an external force of greater than five feet per second (fps) but less than twenty-five fps. Blunt force trauma also produces cast-off blood spatter as blood is thrown from the weapon as it is raised and then brought down on the victim each additional time. This spatter can occur on ceilings, walls and floor depending on the force and direction of the inflicted blows. In the process the victim’s blood is also transferred to the blunt object and can usually be recovery from the weapon once it is identified.
