Wound ballistics and tissue simulants

Flashcards covering key concepts from a lecture on wound ballistics and tissue simulants.

What factors contribute to tissue damage from a bullet?

Tissue damage comes from the energy that the bullet carries, the bullet design, and properties of the tissue impacted.

What is 'tattooing' or 'stippling' in wound ballistics?

The pattern left on the skin from hot gunshot residues embedding into human tissues at close ranges.

What is gas injection trauma in a contact wound?

A distinctive star-shaped splitting of the skin caused by propellant gases being 'injected' between the dermis and cranium.

What can high temperatures associated with a gunshot create on the skin in contact shots?

Burning of class characteristics related to the firearm into the skin around the entry wound.

What are the typical characteristics of shotgun wounds?

Multiple entry wounds and usually no exit wounds, unless shot at very close range. The wadding could become embedded in the wound or at least mark the skin near the wound area.

What is 'bevelling' in skull impacts and why is it important?

A phenomenon where the shape of the bullet hole in the bone can suggest the angle of impact, sometimes the only reliable way of defining entry and/or exit wounds.

What is a 'gutter' wound?

A tangential impact where the projectile impacts the surface of the skull at a relatively shallow angle and does not penetrate, leading to serious external damage.

What is a comminuted fracture and what can they be mistaken for?

Fracture opposite the point of entry, can be mistaken for exit wounds.

What happens to the skull cap following high velocity ballistic trauma?

The skull cap often becomes susceptible to 'popping off' following high velocity ballistic trauma due to the large increase in pressure generated inside the skull.

How do different sized bones react to bullet impacts?

Smaller bones shatter with fragmentation, while larger bones tend to chip and deflect/deform the bullet.

What type of fractures do handguns and rifles tend to create?

Handguns tend to create a 'simple fracture' in bones, while rifles tend to create a 'multi-fragmentary fracture'.

What is the forensic evidence from a bone impact?

The bullet jacket, specifically the rifled segment of the bearing surface.

How can bullet trajectory be determined from a body?

Polycarbonate rods are inserted into the permanent wound cavities and the victim’s body manipulated until the rod passes through, following the path of the bullet to suggest what the victim was doing at the time.

What is the permanent wound cavity?

The path of tissue destroyed by the transit of the bullet formed by the crushing of soft tissues or tearing by shrapnel/fragments, does not completely close and leaves internal tissues exposed to atmospheric contamination.

What is the temporary wound cavity?

Created by projectiles imparting radial acceleration to the tissue, forcing it out laterally during penetration, closes almost immediately after the passage of the bullet.

What must a bullet impact in order to 'stop' the target?

Impacting the central nervous system, or impacting a critical structure, the failure of which induces massive bleeding.

What is a ballistic penetration simulant?

A material that is able to give comparable and reproductive wound data in relation to the human body when penetrated by a projectile.

Why do we use ballistic simulants?

To overcome ethical issues, give comparative data, understand potential wounding effects and give accurate and reproducible data.

What are the desirable properties of soft tissue simulants?

Non-cadaveric, ethically sound, readily available, similarity in deceleration and deformation behavior and kinetic energy dissipation.

What are the difficulties in testing biological materials?

Variability, soft materials, tricky processing, viscoelastic and multi-axial testing is required, requires dynamic properties and ethics.

What is Ballistic Gelatin?

Collagen extracted from bones and sinews of pigs typically used in two formulations for the simulation of soft body tissues such as muscle: 10% gelatin @ 4 °C and 20% gelatin @ 20 °C.

What kind of material is soap and how can it be useful in the observation of wound ballistics?

A 'plastic' (non-elastic) material that allows the 'profile' of the temporary cavity produced during penetration to be observed, used to predict size.

What types of leather are used to simulate human skin for ballistic testing?

Either upholstery or chamois leather that represents collagen in human skin.

What is the future of ballistic simulants?

Increase use of radiography, more research into material properties, validation of systems, modern techniques to collect data and interdisciplinary research.