Section 8: Forensic Overview of Gunshot Wounds

Range of fire: Contact

0-12 inches muzzle imprint

Range of fire: Intermediate

3-5 feet abrasion

range of fire: distance

>5 feet

firearm

Generally defined as an assembly o barrel + action from which projectile is propelled through deflagration (rapid burning) of propellant (gun powder)

skull + bone beveling

In case of head injuries, best form of identifying an exit wound from an entrance is looking @ beveling of skull in bullet path This can be used, for other areas of body as well where bone is impacted (ribs, sternum, scapula, other large flat bones)

exit wound

Irregular, has no abrasion rim, + don't display soot deposition/ stippling They may have stellate configurations, particularly in event of low velocity exit wounds have slit like configuration These can be deceptively sharp appearing + can mimic stab wound

why GSR info is important

Not so much as who fired the weapon, though certainly helps in determining this More importantly it will determine who was is close proximity when a gun was fire If husband was not home, why is GSR on his hands / clothes ... ?!?!? GSR collection + clothing should be taken from all present, reporting,/ who otherwise could be involved

Trajectory of a projectile

Path followed by projectile flying/ an object moving under action of given forces trajectory/ direction of a projectile through the body may be approximated but it must be kept in mind that this doesn't necessarily equate to trajectory of bullet through space B/C the bodies of the victim + shooter aren't static + may move about in 3D during a shooting event

when GSR may not help

Prior handling of gun GSR on decedent Not always found in testing

wound interpretation

Various types of firearms may produce wounds that have characteristics reflective of the type of weapon inflicting the injury. However, many characteristics of firearm wounds are similar across a range of weapons

penetrating

an object enters the body or structure + doesn't pass through bullet still inside body

range of fire

based on characteristics of firearm wound, features of wound that have been imparted by material coming from the muzzle of firearm other than the bullet, or from features due to interaction between target + firearm itself

spatter

blood stain, gives investigator indication of direction + velocity blood struck surface can be important when reconstructing crime scene/ verifying witness statements often times fine mist blood will exit the body upon impact by bullet this mist can be deposited on shooter during a close-range shooting

gun scene investigation

care should be taken not to disturb blood pattern on floor or walls, as they may give indication as to the site of injury + degree of activity of decedent after injury

percussion injuries

caused by expansion of skull or enclosed space of body due to introduction of gas pressure may cause some entrance wounds to appear as existed if the skin is grossly lacerated racoon eye

stippling + tattooing

caused from burnt + unburnt powder hitting the skin + marking or staining skin

gunshot residue

firing weapon produces combustion of both primer + powder of cartridge residue of combustion products consist of both burned + unburned primer + powder + can be used to direct cartridge found on skin or clothing of person who fired gun, on materials @ scene on their target materials @ scene

its not uncommon

for a person to survive a firearm wound, eventually succumbing to remote complications of the wound weeks, months,/ even years later. However, such a case remains of medicolegal interest if it can be shown to be directly/ indirectly related to initial wound

abrasion ring

formed when the force of the gases entering below the skin surface back against the muzzle of the gun

forensic scene investigation

if firearm primer residue sampling is desired, it may be collected @ scene, or hands may be covered by paper bag before transport The presence of bullet strikes on the wall of the room should be notes, as these can serve as reference points for later reconstruction of the position of a shooter when combined w/ trajectory through the body

range of fire importance

issues of whether a wound is self-inflicted or inflicted by others, the truth of stated explanations of shooting events, + validity of self-defense arguments

gunshot residue major primer elements

lead (Pb) barium (Ba) antimony(Sb)

general type of weapon

may sometimes be determined by the characteristics of wound, + by recovery of projectile causing wound, w/ appropriate analysis

materials from muzzle

may take the form of soot, hot gas, gunpowder particles or other materials

bullets can do odd things when entering or exiting a body

more than 1 entrance from 1 bullet deflection entrance (ricochet) shin may seal over oblong or sideway entry fragment exit

entrance v. exit

never assume you know an entrance from an exit some characteristics are common but many factors can change wound types assumption might change the entire investigation

perforating

object enters the body + passes all the way through bullet at the scene or in clothing

trajectory info caution

occasionally the pathway of a bullet the body may give some indication of the actual position of body when shot

wound types

penetrating perforating

aspects of firearm wounds

range of fire type of wound trajectory extent of injuries

smoke + soot Gunshot residue

residue on skin from smoke + smoot produced from burnt gunpowder

investigating firearm injuries

resulting in death will fall into manner of homicide, suicide, / accident, all will come under the jurisdiction of a ME/ Coroner + local LE Injuries not resulting in death will remain the jurisdiction of local LE.

trajectory/ path of a pullet needs to be determined by using

rods lasers string Attach to bullet holes to see where shooter was @ Rods to track bullet trajectory through the brain

position + location of firearm

should be carefully noted, if present, + if firearm is loaded in a round chamber, are fired rounds in cylinder Any projectile found beneath decedent, stuck to clothing,/ other areas should be photographed + recovered @ time to prevent possibility of loss during transport

abrasion with muzzle imprint

the abrasion ring + very clear muzzle imprint, are seen in this contact range gunshot wound

general characteristics

type/ brand of firearm may be determined but these features are still useful. Importance + necessity of recovery retained projectiles should be understood, considering potential wealth of info that may be cleaned from their examination

entrance wounds

typically round or oval, with smooth edges + zone of epidermal abrasion surrounding wound edge this abrasion is caused by rubbing or scraping of surrounding skin surfaces by bullets as it indents the skin before perforating it

internal beveling

where inner surface of skull is more eroded than outer surface, producing "cone" shape in direction of bullet path

range of fire determination will answer

who shot who? could it have happened the way witnesses are saying?

wound type + interpretation is important to

your investigation as it will prove a witness/ suspect statement true/false, + help "tell the story" of the incident