Topic 11 - Wound Ballistics & Tissue Simulants Flashcards
Where does tissue damage come from?
Energy, properties
Tissue damage comes from the energy that the bullet carries, the bullet design and the properties of the tissue that is impacted.
What can shootings at a close range leave on a body?
Shootings at close range can leave distinctive marks on the body.
What are the majority of civilian firearm wounds caused by?
The majority of civilian firearm wounds are inflicted at close to medium range (0 to 25 m), usually with handguns.
What is possible to analyse at very close range? (wounding)
Cell & tissue damage, deposits & patterns
- At very close range it is possible to analyse not just the tissue damage, but also propellant deposits and burn patterns.
- Contact wounds will almost always leave a mark or imprint.
- Even if the contact is light, the metal of the firearm on the skin will cause cell damage at the point of contact
What is tattooing/stippling?
Residues + close range
- Hot gunshot residues can embed into human tissues at relatively close ranges and leaves a pattern on the skin.
- This can be easily mistaken for shotgun wounds by the untrained eye.
What can give an indication of the incidence angle?
The distribution and shape of the pattern could also give an indication of incidence angle.
When are GSR left on skin recoverable?
Gunshot residues are recoverable from skin around a wound for close range shooting (less than a few metres)
What can a contact shot to the head lead to?
A contact shot to the head can lead to a distinctive star-shaped (stellate) splitting of the skin.
Why can a contact shot to the head leave a specific mark?
The propellant gases are ‘injected’ between dermis and cranium but have nowhere else to go, so they escape to the external environment by bursting out of the skin surrounding the wound.
What leads to the burning of class characteristics related to the firearm into skin?
High temperatures associated, imprint, markings
- The high temperatures associated with the shot permit the burning of class characteristics related to the firearm into the skin for contact shots.
- This can lead to an imprint of the muzzle and fore-end around entry wound.
- Manufacturer markings may also be visible around wound.
What is typical for intermediate and long-range wounds?
Muzzle imprint, Penetration data
- No muzzle imprint or gas injection trauma.
- Minimal or complete absence of tattooing and GSR collection not possible.
- Penetration data alone cannot be used to appreciate the range as this is dependent on too many factors.
What is typical for shotgun wounds?
Wadding
- Shotgun wounds typically exhibit multiple entry wounds, dependant upon ammunition type.
- Unless shot at very close range, there are usually no exit wounds.
- The wadding could become embedded in the wound or at least mark the skin near the wound area.
What do skull impacts often result in?
Exit & entry wounds
- Skull impacts will often result in a phenomenon called ‘bevelling’.
- This is sometimes the only reliable way of defining entry and/or exit wounds.
- The bullet will often remain intact, albeit deformed, after a skull impact.
What can the shape of the bullet hole in the skull suggest?
- Shape of the bullet hole in the bone can suggest the angle of impact.
- For example “key-holing” from acute angle impacts as opposed to circular for perpendicular
impacts.
What is a gutter wound and what damage can it cause?
Shallow angle, internal damage
- The projectile may impact the surface of the skull at a relatively shallow angle and not penetrate – a tangential impact.
- This can create a so-called “Gutter” wound leading to serious external damage.
- The internal damage can be variable, depending on the creation of secondary projectiles or energy transfer that can affect the brain material.
What causes a comminuted fracture?
Acute angled impacts
- Acute angled impacts can be deflected within the cranial cavity, causing a comminuted fracture diametrically opposite point of entry.
- The bullet is recoverable by a pathologist or surgeon; rifling mark data should be intact.
- Comminuted fractures can be mistaken for exit wounds – termed a pseudo-exit wound.
What is the calvaria (skull cap) often susceptible to?
High velocity
The skull cap (calvaria) is often susceptible to “popping off” following high-velocity ballistic trauma.
What causes the ‘popping off’ of the calvaria?
Increase in pressure, high energy transfer
- The is due to the large increase in pressure generated inside the skull following a high energy transfer to the brain material.
- The brain material is pushed out radially from the projectile’s path in a phenomenon known as the “temporary cavity”.
- In other incidents, this process could affect different bones in the body if they are adjacent to a temporary cavity being produced.
What happens to smaller bones when they get damaged by a bullet?
Smaller bones such as the radius/ulna or clavicle will shatter with fragmentation extending beyond the damaged area
What happens to larger bones when they get damaged by a bullet?
- Larger bones such as the femur or pelvis will tend to chip and deflect/deform the bullet.
- In extreme cases the bullet may shatter or, if jacketed, drop its core.
What wounding do low-energy transfer weapons cause?
- Handguns tend to have a lower average projectile energy on impact and therefore have less energy to transfer upon direct impact with bone.
- Typically 500-800 Joules.
- This often creates a “simple fracture” in bones, particularly long bones – a single break leaving just two main pieces.
What wounding do high-energy transfer weapons cause?
- Rifles tend to present a higher average projectile energy on impact and therefore have more energy to transfer upon direct impact with bone.
- Typically 1800-7000 Joules.
- This often creates a “multi-fragmentary fracture” in bones, particularly long bones, with several breaks and widespread fragmentation.
- Also creates “secondary missiles”
