The following is a brief summary of the modern explanation of gunshot wounds according to the proponents of interpreting gunshot wounds (GSW).  After you read this, you draw your own conclusions as to whether or not this is empirical or more towards the subjective or non-validated.

Typical GSW explanation in Court

Typical GSW explanation in Court

Gunshot Wounds:  A summary form a pathology textbook

In general, when a person is shot, the injury sustained will result in a temporary wound cavity that is produced due to cavitation, which occurs when a body moves so quickly in a liquid that the liquid detaches from the body surface. This cavity will only exist for a short period of time after the penetration of the projectile. The size and seriousness of the wound cavity will depend on the amount of energy transmitted by the gun, which is dependent on the length of the barrel; the longer the barrel, the greater velocity.

There are four categories of wounds:  (1) contact wounds, which can be hard, loose, angled or incomplete; (2) near contact; (3) intermediate; and (4) distant.

GSW wound interpretation from a pathology treatise

Typical GSW wound interpretation from a pathology treatise


When the wound is a contact wound the muzzle of the gun is placed up against the body at the time of discharge. When this occurs gas, soot, metallic particles, vaporized metal, primer residue, and powder particles can be found in the wound track. Hard contact wounds result from the muzzle being held very tightly against the skin and will create an indent. Due to the closeness of the muzzle to the skin, all the materials from the muzzle will be left directly in the wound which leaves very little external evidence on the skin. If a proper autopsy was conducted soot and un-burnt particles would be found in the wound track. During the autopsy soot could easily be distinguishable from dried blood as soot, unlike dried blood, cannot be removed by either water or hydrogen peroxide.  Furthermore, if a dissecting microscope was used, not only would soot always be present in the wound, but also the powder particles left in the wound could be identified.

Where the projectile pierces skin that is tightly flexed over bone, like the skull, the wound will have a different appearance because the gas discharge, which expands between the skin and outer table of the bone, lifts the skin and causes it to “balloon out”. When the stretching of the skin exceeds the elasticity of the skin, the skin will tear. The subsequent size of the tear will depend on the caliber of the weapon used, the amount of gas produced, the firmness of the weapon held to the body, and the elasticity of the skin. This type of tear, however, can also occur when the victim is shot at an intermediate or distant range if the bullet is able to perforate the skin over a bony prominence or curved area of bone that is covered by a thin layer of tightly stretched skin.

Where gas is the cause of the tearing of the skin, however, the detail of the imprint left on the skin will depend on the amount of gas produced from the firing of the gun. The more gas produced, the harder the skin will impact against the muzzle, which results in a greater, more detailed imprint. Imprints cannot only be found on the skin but will be found in the chest and the abdominal region as well because the gas produced will expand in the visceral cavities and adjacent soft tissue causing the chest or abdominal wall to bulge out creating larger imprints which can be twice the actual size of the muzzle.

The presence of a loose contact wound suggests that the muzzle is held in very light contact with the skin as the skin is not indented by the muzzle. In this type of situation, the gas preceding the bullet and the actual bullet itself will be the cause of the indent on the skin. Any soot left on the skin can be easily swiped away but an autopsy can and will reveal particles of powder, vaporized metals, and soot deposited in the wound track, along with carbon monoxide.

An example of sooting and stippling
An example of sooting and stippling

In near contact wounds, the second category, clumps of unburned power can pile up on the edges of the entrance wound and on the seared zone of the skin.

The third category, intermediate wounds, are formed when the muzzle is held away from the body at the time of discharge but is still sufficiently close enough that the powder grains from the muzzle can strike the skin and produce powder tattooing, which gets it name from the blackening of the skin around the entrance site caused from the soot. The size and density of these tattoos will depend on the caliber, barrel length, type of propellant powder, and the distance from the muzzle to the target. As the range away from the target increases, the intensity of powder blackening will decrease and the size of the soot pattern area will increase. The powder tattoo which results is unlike the soot in the loose contact wound in that it cannot be swiped away from the skin.

Finally, distant wounds, will be created when the muzzle is sufficiently far from the body so that there is neither deposition of soot nor powder tattooing in the wound track. When a person is shot from a distance, the clothing of that individual will absorb the soot and the powder, thus making it essential for the victim’s clothing to be examined during the autopsy. As the clothing absorbs most, if not all of the soot, the ability of the powder to leave a mark on the skin of the victim will depend on the nature of the material, the number of layers of cloth, and the physical form of the powder.

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Blogger’s comments:

The problem with these types of descriptive groupings lies in the validation.  These definitions and descriptions of observable phenomena sounds scientific, but is it?  It sounds like something that is empirically based, but is it?  How is it possibly measured?  How are these conclusions validated?  How can we have confidence that these categories and the underlying observations that describe them are unique as to that category and not present in the other categories?  We can’t.

Some of the problem comes down to one of the very basics:  documentation.  Usually in autopsies, photographs are taken.  Sometimes they are not taken according to basic principles of photogrammetry.  The photos are taken from oblique angles instead of at 90 degrees and most of them have no scaling mechanism.  This lack of meaningful photography makes it difficult to verify measurements taken, produce any sort of scale or otherwise reconstruct the wound characteristics.  In addition how the investigator approaches documenting the wound can drastically change the interpretation.  For example, if one were to clean the wound site or shave it with the idea of revealing it, then gun shot particles, sooting or other characteristics may be removed.  In addition, some examiners still use metal rods to try to determine the “path of the bullet” by probing the wound and inserting rods through it.  This will deform and alter the organic state of the wound.  In the worst case scenario, it can actually create a false path through soft tissue and therefore lead to an erroneous conclusion.  Rather than just relying on the typical “I know it when I see it” characteristics outlined above that is used in modern gunshot wound examination, we should use computerized tomography, fluoroscopy and even radiographs including CAT scans.

Head computed tomography (CT) scout image of a patient who suffered a gunshot wound to the head.

Head computed tomography (CT) scout image of a patient who suffered a gunshot wound to the head.

Axial computed tomography image of the chest in a patient with a gunshot wound. Note the comminuted rib fracture (black arrow). A lung contusion is present along the path of the bullet (yellow arrow). A chest tube was placed to treat the right pneumothorax.

Axial computed tomography image of the chest in a patient with a gunshot wound. Note the comminuted rib fracture (black arrow). A lung contusion is present along the path of the bullet (yellow arrow). A chest tube was placed to treat the right pneumothorax.

A 65-year-old man experienced a gunshot wound to the right frontoparietal region. A CT scan shows that the bullet crossed the midline, lacerated the superior longitudinal sinus, and produced a large midline subdural hematoma. The patient presented with a Glasgow Coma Scale (GCS) score of 4 and died.

A 65-year-old man experienced a gunshot wound to the right frontoparietal region. A CT scan shows that the bullet crossed the midline, lacerated the superior longitudinal sinus, and produced a large midline subdural hematoma. The patient presented with a Glasgow Coma Scale (GCS) score of 4 and died.

Now, after seeing these computerized tomography images, who can argue with what is more persuasive, “I know it when I see it” or the available science?

 

Medical Examiners and Autopsy: the irretrievable action

The Anatomy Lesson of Dr. Nicolaes Tulp, by Rembrandt, depicts an autopsy.

The Anatomy Lesson of Dr. Nicolaes Tulp, by Rembrandt, depicts an autopsy.

An autopsy is a scary thing for the citizen accused of a homicide.  This is due to the fact that performing an autopsy is a horribly destructive act.  Once you make an incision, it is there.  There is no healing.  Once you reflect back the scalp, then it cannot be put back together.  Once the brain is severed and removed, it cannot be returned.  All of the kings horses and all of the kings men cannot put the decedent back together again.

a large and deep Y-shaped incision can be made starting at the top of each shoulder and running down the front of the chest, meeting at the lower point of the sternum. This is the approach most often used in forensic autopsies so as to allow maximum exposure of the neck structures for later detailed examination.

A large and deep Y-shaped incision can be made starting at the top of each shoulder and running down the front of the chest, meeting at the lower point of the sternum. This is the approach most often used in forensic autopsies so as to allow maximum exposure of the neck structures for later detailed examination.

The difficulty in the modern way that we perform autopsies is that a poorly documented and/or poorly performed autopsy will lead to the irrevocable and irreparable destruction of evidence.  It cannot be meaningfully examined again as the body cannot be returned to its pre-autopsy state.  You only get one chance to do it right.

Forensic Autopsies are destructive acts

Forensic Autopsies are destructive acts

This has been a long time criticism of autopsies.  The scientific community is starting to acknowledge that there is a greater need to try to find non-evasive or less evasive alternatives to get meaningful and useful data.  This largely surrounds medical imaging techniques.