Forensic Science - How Does a Medical Examiner Differentiate Between an Entrance and Exit Wound?

Whenever a shooting occurs and police are called to investigate a dead body as a result of the shooting, crime scene investigators (CSI's) will come to process the scene. The medical examiner will then determine where the bullet entered; if possible, where it exited; and what caliber bullet, or bullet diameter, was used to kill the victim.

In this article, I will define what entry and exit wounds are and what the characteristics are that make up an entry wound.

When a bullet enters a person, it leaves behind what is called an entry wound. However, that bullet will not necessarily leave another hole called an exit wound when the bullet exits the body. Often times, the bullet stays inside the victim's body. When evaluating gunshot wounds, a medical examiner looks for entry and exit wounds and tries to find any bullets still lodged inside the victim. Even though the distinction is not always evident, the medical examiner also tries to determine the difference between entry and exit wounds, because doing so can be crucial in rebuilding the scene of a crime. Knowing the trajectory, or path, of a bullet can incriminate or exculpate suspects or help determine which projectile caused the mortal wound.

The characteristics of a bullet wound are a function of several factors:

• The distance between the muzzle, or end of a gun's barrel, of the gun and the victim.


• The caliber, or diameter, and velocity of the bullet.


• The angle at which the projectile enters the body.


• Whether the bullet stays inside the victim or passes through, leaving, or exiting, the body. Hence the term, through-and-through gunshot wound.

A medical examiner can determine the distance from which a single projectile was fired by examining closely the bullet's point of entry. The characteristics of those entries are as follows:

• If the muzzle was two (2) or more feet away from the victim, the entrance wound ordinarily is a small hole, accompanied by an abrasion collar. An abrasion collar is a blue-black bruising effect in a halo surrounding the entrance wound. Some black soot may be left behind on the skin when the skin literally wipes the bullet clean as it passes into the victim at the entrance wound.


• If the muzzle was between six (6) inches and two (2) feet from the point of entry, the skin may have a tattooed, or spotted, appearance. This tattooed appearance is the result when tiny particles of gunpowder discharged from the muzzle embed themselves in the skin, producing tiny red dots of blood inside the skin in a speckled pattern around the wound.


• If the muzzle was less than six (6) inches from the victim, the gunshot produces a hole, a small area of spotting, an encircling area of charring, and a bright red color to the wounded tissues.


• If the muzzle is pressed against the victim when the gun is discharged, hot gases and tiny particles are driven right into the skin, producing greater charring and ripping the skin in a star-like, or stellate, pattern.

In general, exit wounds typically are larger in size than entry wounds because of the fact that the bullet cuts or tears the soft tissues as it forces its way up and out through the skin. The size and shape of the exit wound depend on the caliber, speed, and shape of the bullet. For example, soft lead bullets are easily misshapened as they enter and pass through the body, especially if they hit any bony structures along the way. When that occurs, the bullet may became grossly deformed, which, in turn, produces more extensive tissue damage in its wake and many times results in an irregular, gaping exit wound.

Determining the difference between entry wounds and exit wounds is not always simple for the medical examiner, especially when the exit wound is shored. Shored refers to when clothing or some other material provides support to the wound. The ragged attribute of many exit wounds is caused by the bullet tearing its way through the skin. However, if the victim's skin is supported by tight clothing or the victim is against a wall or other structure, the skin is less likely to tear. The exit wound therefore will be smaller and less ragged. It will take on the resemblance of an entry wound.

The next time you watch NCIS or your favorite CSI TV program, you will be better knowledgeable about the terminologies used when criminalists investigate a gunshot victim.

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