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