1
Q
Tattooing
A
- Hot gunshot residues can embed into human tissue at close ranges
- The distribution and shape of the pattern can also give an indication of the incidence angle
2
Q
Contact wound - gas injection trauma
A
- A contact shot to the head can lead to a distinctive star-shaped (stellate) splitting of the skin
- The propellant gases are injected between the dermis and cranium but have nowhere else to go so they escape to the external environment by bursting out of the skin surround the wound
3
Q
Contact wound - muzzle imprint
A
- The high temperatures associated with the shot permit burning of class characteristics related to the firearm into the skin for contact shots
- Manufacturer markings may also be visible around the wound
4
Q
Intermediate and long range wounds
A
- No muzzle imprint or gas injection trauma
- Minimal or complete absence of tattooing and GSR collection not possible
- Almost impossible to estimate range of shot accurately
- Sonic and echo data could indicate position of shot
5
Q
Skull impacts
A
- Bevelling - smooth entry wound, but exit wound has a cone like shape
- Shape of the bullet hole in the bone can suggest the agle of impact
- Gutter wound - where the projectile impacts the surface of the skull at a relatively shallow angle and doesnt penetrate (tangential impact)
- Comminuted fracture - acute angled imacts can be deflected within the cranial cavity causing a communited fracture opposite the entry wound, often misten for exit wounds
- Skull cap can pop off due to large increase in pressure generated inside the skull following high energy transfer to the brain material
6
Q
Low energy transfer wound
A
- Handguns often produce this type of wound as they have a lower average projectile enrgy on impact
- Often creates a simple fracture particularly in long bones - single break leaving two main pieces
7
Q
High energy transfer wound
A
- Rifles tend to have higher average projectile energy on impact
- Creates a multi-fragmentary fracture
- Also creates secondary missiles from the bone fragments
8
Q
The permanent wound cavity
A
- The path of tissue destroyed by the transit of the bullet and is formed by the crushing of soft tissues or tearing by shrapnel/fragments
- This cavity does not close completely after the passage of the projectile and leaves the internal tissues exposed to atmospheric contamination
- The size is closely related to the bullets caliber
9
Q
The temporary wound cavity
What is it and how is it formed
A
- Soft tissue will be damaged slightly but natural tissue elasticity will cause the cavity to close almost immediately after the passage of the bullet
- Less elastic tissues are not able to withstand the process and will be deformed permanently (permanent wound cavity)
- More kinetic energy of the projectile the larger the temporary cavity
1. Projectiles imparting radial acceleration to the tissue, forcing it out laterally during penetration
2. The kinetic energy passed into the moving elastic tissue is transformed into strain energy
3. Upon the cavity growth halting and reaching its max diameter, the strain energy almost instantaneously is released causing it to return to its original position
4. This process assumes that the elastic limit is not surpassed
10
Q
Things that can be used as soft tissue simulants
A
- Gelatin - can be used to show temporary cavities
- Soap - allows you to see the profile of the temporary cavity, not a direct representation of that expected in human tissue
- Leather - used to simulate skin
11
Q
Reproducibility problems for simulants
A
- Any biological organism is likely to be different from another, and so a given biological tissue is unlike any other and there is no standard figure attributable to any material property of the tissue
- Averaged values comprise a very high associated error
- Sample prep is tricky
- Ethics
- Most standard methods cannot be used as materials are too soft
