Blunt Versus Sharp Force Injuries: A Primer on Terminology

Often in casual conversation (and even in medical records) all open skin wounds are called “lacerations,” despite the fact that this term has a fairly narrow definition. Forensic pathologists need to be very particular about using correct terminology for injuries. Different types of injuries correspond to different mechanisms of injury, which can have real consequences for an ongoing investigation. Excluding gunshot wounds, (a separate wound type that requires its own blog post), the other main categories of trauma are blunt and sharp force injuries. Blunt injuries are inflicted by dull objects, whereas sharp force injuries are inflicted by a blade or other edged object. Chop wounds, less commonly encountered in practice, have features of both.

Blunt Force Injuries

There are three cutaneous manifestations of blunt impacts. An abrasion is the equivalent of a scrape, wherein the superficial skin layer is removed. A contusion refers to a bruise, in which there is hemorrhage in the skin and subcutaneous tissue. Finally, lacerations occur when the skin and underlying tissues are crushed and tear apart from each other, resulting in an open wound. Neurovascular bundles in the subcutaneous tissue have high resistance to crushing forces and remain intact, resulting in characteristic “tissue bridging” within the wound depths. The edges of lacerations are often abraded, as well. Because blunt force injuries result from direct application of force, the object involved can impart a pattern onto the skin, or deposit potential trace evidence (hair, fibers, paint chips). It’s always important to look for patterns and try to correlate injuries with scene findings. If a patterned (or suspected patterned) injury is found at autopsy, scale photographs must be taken with a specific ruler (the ABFO ruler), to produce scale photographs for comparison if the object is found.

Deaths related to blunt force injuries can be accidental, suicidal, or homicidal in nature, and cover a wide variety of situations. Motor vehicle accidents, falls or jumps from heights, and homicidal beatings are all situations where the cause of death is blunt force injuries. Each of these situations have particular wound patterns that forensic pathologists are trained to recognize.

Sharp Force Injuries

Sharp injuries can be divided into stab wounds or incised/cutting wounds. The difference is wound dimensions: stab wounds are deeper than they are long, and incised wounds are longer than they are deep. In contrast to lacerations, sharp forces cleanly transect all tissues including neurovascular bundles, meaning stab and incised wounds show no tissue bridging. As mentioned in the first paragraph, distinguishing a laceration from a cut made with a blade can be critical. Mis-identifying a laceration as a “cut” or “stab,” or vice versa, may send law enforcement down the wrong path. Similar to blunt force, deaths by sharp force can be accidental, suicidal, or homicidal, although in my experience accidental deaths by sharp force are extremely rare.

These categories make the definitions sound clear-cut (no pun intended), but it’s important to keep in mind that in actual practice, as with everything else in medicine, unusual situations occur. ‘Chop’ wounds have features of both sharp and blunt force and are typically inflicted by a heavy object with an edge (like an axe or propeller blade). As one example, a beating with a hatchet or machete may cause sharp, blunt, or chop wounds, depending on the sharpness of the blade and what part of the weapon impacts the body. Even when an unusual object is used as a weapon, recognizing the different components of a wound and any patterns imparted on the skin can help guide an investigation.