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

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.

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.

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.

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.

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?