1. Gunshot Wound Interpretation
Identification and classification of gunshot wounds

2. Typical Gunshot Wound Morphology

3. Analysis of Projectile Wounds
Variability of ammunition and firearms and their effect in bone should make us cautious during interpretation and descriptions should be in general terms

4. WOUND TYPES
PENETRATING - the bullet enters the body but does not exit (entrance wound only)
PERFORATING - the bullet enters and exits the body (entrance and exit wounds)

5. Wipe
Bullet holes of entrance in the skin might have a grey coloration to the abrasion ring.
More typical in clothing (called bullet wipe)
It consists of soot deposited on the surface of the bullet as it moves through the barrel
NOT same as powder soot present in contact wounds

6. Powder Soot
Comes out from the muzzle, produced by combustion of gunpowder that vaporized metals from the primer, bullet and cartridge.
It embeds in tight contact wounds marking it black, cannot be washed off. In loose contact it can.
Distance increases the stained area

7. Powder Tattooing
Diagnostic of intermediate range wounds when shown individually.
Powder grains do not have time to disperse and mark the skin (they are not powder burns, but rather punctuate abrasions) (Not the same as powder soot)
They are numerous reddish-brown to orange-red punctures surrounding the entrance wound

8. CLASSIFICATIONS OF GSW (range of fire)
CONTACT - muzzle is in full contact with the skin at time of discharge
They maybe hard, loose, angled, or incomplete.

9. Contact: bulb of percussion creating larger exit hole, powder and smoke deposited into wound, stellate scarring
stellation of tissues,
scorching,
tissue delamination,
bruising by firearm part,
powder in wound track,
tissue blowback onto firearm,
gas damage from high velocity firearms.

10. CLASSIFICATIONS OF GSW
NEAR CONTACT - muzzle not physically touching the skin, but within 10 mm
Powder grains emerging from the muzzle do not have chance to disperse and mark the skin, producing powder tattooing (not individual grains)
Entrance wound surrounded by a wide zone of powder soot overlying seared, blackened skin

11. Near Contact depositing smoke and powder

12. CLASSIFICATIONS OF GSW
INTERMEDIATE RANGE - (GREATER THAN 10 mm) - tattooing of gunpowder is the hallmark (individual tattoo marks).

13. CLASSIFICATIONS OF GSW
DISTANT (LONG RANGE) - only marks on skin created by perforating bullet

14. Caliber Determination from Entrance Wounds
EXACT DETERMINATION CANNOT BE DONE
size of the hole is related not only to caliber but also to the elasticity of the tissue and the location of the wound
-on average min. diameter holes are about mm bigger than caliber

15. Identifying Entrance and Exit Wound
Trajectory of bullet seen in outward beveling of the wound
Bullet “punches out” an entrance, leaving a smooth round hole and “blows out” an exit
Presence of wipe also indicates direction of bullet
Exit wounds are larger than entrance wounds due to two factors: spin that stabilizes the bullet no longer holds due to tissue resistance. Increasing its yaw. 2.- bullet may be deformed in its passage through body. Both conditions increase the size of the bullet as it exits the body
Beveling … why?

16. Funnel effect

17. Entrance wound Skull: round wound; usually due
To angle of trajectory and angle of bullet axis are
Perpendicular to bone surface … what kind of
Bullet would cause a round EXIT wound …?
Notice: reverse
beveling

18. Exit wound of entrance

19. Estimation of Sequence
Locate entrance and exit wounds
Distinguish radiating from concentring fx.
Follow radiating fractures from beginning to end, if this fx line ends in another, this one is later in the sequence than the fx where it stops
ID the entrance wound whose fx do not end in another and you have the 1st. Shot
They might miss each other, impossible to
Estimate sequence.

20. Atypical Gunshot Wound Morphology

21. Keyhole entrance wound

22. Keyhole Defects
Occurs when the bullet strikes the skull at an angle, splitting into two or more fragments
Produced an entrance wound that is externally beveled
Possible to infer direction of fire: the round part of the defect with inward beveling points to the placement of the weapon at time of fire.
Entrance and exit wound in one

23. Shored Exits
Changes to the exit wound which could mimic the appearance of an entrance wound
Exit wounds with abraded margins (which is typical of entrance wounds). Occurs when a firm surface (or tight garments) is at site of exit the bullet everts the skin which in turn impacts against the firm surface abrading the area everted.

24. Interposed GSW
Occurs when the bullet passes through another object (glass –stippling- ), car door) before entering the victim
Frequently seen in drive-by shootings
Differentiated from ricochets or deflected bullets
Bullet no longer follows predictable trajectory and loses kinetic energy with first contact

25. Morphology of Shotgun Wounds
Differences in projectiles and gas combustion
Soot/wipe deposit differs from hand guns/rifles

26. External Ballistics

27. THREE MAJOR FACTORS
1) VELOCITY
2) DISTANCE
3) TISSUE TYPE

28. TERMINAL BALLISTICS
When a bullet passes through a body, it transfers its kinetic energy to the surrounding tissue, creating a temporary cavity and a permanent wound track

29. CAVITATION
The temporary expansion of tissues as the result of the transfer of energy from the bullet to the tissues
Amount of cavitation is dependent on 1) energy, size and type of bullet, 2) elasticity of tissue, 3) distance and velocity
2 types of cavitation: permanent which roughly equals diameter of projectile
Temporary greater pressure around the permanent cavity …. Which can Fx bone w/o touching it.

30. WEAPON VELOCITY
Since the amount of damage caused by the bullet is due to the transfer of kinetic energy - the higher the velocity, the greater the damage
PISTOLS <DAMAGE> HIGH-POWER RIFLES

31. VELOCITY/TISSUE TYPES/DISTANCE
The severity of the wound is directly related to the amount of kinetic energy lost in the tissue, not the total energy possessed by the bullet
(VJM DiMaio, 1985)

32. High Velocity Weapons
More prone to produce concentric and radiating fx.,
And catastrophic shattering of the skull

33. Projectile Vs. Shrapnel
Projectile: object expelled under explosive pressure (bullet)
Shrapnel: explosive force fragments object and produces airborne debris

34. Notice radiating fractures.
Originate from point of impact and moved outwards on any direction, especially weak areas,
Might encounter other fx or sutures where they will dissipate their force
Concentring fx: part of a circle where
Centre is point of impact. Created by
Intracranial pressure created by
Bullet.
Can occur in same injury, later in the
Sequence will stop at radiating Fx.
Direction of fire?