Analysis

Ballistic Gel

The analysis of ballistic gel has two main categories; penetration analysis and fracture analysis. Penetration analysis looks at the distance a projectile has penetrated into the gel and fracture analysis looks at the areas of broken (fractured) gel within a block to find out how much energy was imparted into the block. These are used together with the path of the projectile to understand the severity of a penetrating injury.

1. Penetration: This refers to how deep the projectile penetrates into the target. Factors such as projectile design, material and velocity can influence penetration depth. The below table shows the “assumed” injury classifications.

2. Fracture: Certain types of projectile, such as hollow point or soft point bullets, are designed to expand upon impact. This expansion increases the surface area of the bullet, causing more tissue damage and potentially increasing stopping power within ballistic gel (and ballistic soap) this creates a temporary cavity (that collapses) and a permanent wound cavity which show the resulting wound. Conversely this rapid expansion can decrease the penetration depth. These characteristics create different types of temporary wound cavity, which after it collapses leaves fracture marks within the gel showing at what depth a cavity was created and for how far along the wound path it was sustained.

• Low Expansion:  Low expansion wounds (with high velocity) can be deep penetrating and exit the rear of a target. This is due to the projectile not deforming thus retaining excess energy which has not been imparted into the target.

• High Expansion - High expansion wounds generally penetrate shallower than low expansion wounds with rapid energy loss through deforming and/or tumbling projectiles, increasing it’s resistance within the target thus imparting more energy and more disruption to blood vessels and organs. In gel this is displayed as fractures as the temporary wound expands and collapses behind the projectile.

• Fragmentation - Some projectiles, particularly high-velocity rifle rounds, may fragment upon impact. This means that the projectile breaks apart into smaller pieces, increasing the likelihood of causing severe and multiple injuries. This is either by design or tumbling. The path of the wound(s) can ‘yaw’ in different directions away from the main wound path.

Ballistic Soap

The analysis of ballistic soap is similar in a number of ways to ballistic gel with penetration and fracture analysis, however the plastic deformation characteristic of ballistic soap means that the temporary ‘cavity’ that collapses in ballistic gel remains intact within the ballistic soap. This provides you with additional analytical capabilities and insights when interpreting the results of your tests. in this case we refer to ‘fracture’ analysis as ‘cavity’ analysis. Additionally there is a third type of analysis which is energy for this type of analogue.

Penetration: Refer to the table above under the ballistic gel heading.

Cavity: Following the same principles as within the ballistic gel fracture analysis, similar wounds are created. The diagrams within the ballistic gel fracture analysis can be considered as accurate representations as what is seen within the ballistic soap.

Energy: Energy analysis is calculating an estimate for the amount of energy that has been transferred into the ballistic gel from the projectile. After firing into the ballistic soap, there are three options available for analysing the energy:

i. Estimated volume: To determine the estimated volume, you need to cut the block in two along the wound track and measure the internal dimensions on one side (assuming both sides are equal. This method allows you to preserve the block and the wound in the best possible condition. Measure the length (a), height (h) and apply the formula: Volume = V = (π * h * a^2) / 3

Where:

V = Volume of the lanceoloid

π = Pi, approximately 3.14159

h = Height of the lanceoloid (the distance between the two pointed ends)

a = Length of the lanceoloid (the distance between the two widest points)

Method:

i. Measure the height (h) of the lanceoloid.

ii. Measure the length (a) of the lanceoloid.

iii. Square the value of a (a^2).

iv. Multiply the squared value of a by Pi (π).

v. Multiply the result by the height (h).

vi. Divide the final result by 3.

ii. Water volume: By turning the block on its end, you can temporarily fill it with water until it reaches the top. Then, pour out the water and measure its volume or weight. If the projectile passed through the block, you should cover the exit hole and fill the block from the entry hole. Note that this will cause issues if you would like to keep the wound shape in the ballistic soap if the water is kept in the ballistic soap for any period.

iii. Casting volume: Similar to the water volume method, you turn the block on its end and temporarily fill it with casting plaster until it reaches the top. Once the plaster sets, you can cut out the casting from the ballistic soap. If the projectile passed through the block, cover the exit hole and fill the block from the entry hole.

It's important to note that if the projectile completely passed through the block without another block to continue capturing the energy transfer, the final calculation will subtract this amount. Usually, this subtraction is negligible. However, if you need to accurately calculate the energy, it is recommended to use a second block. If using a second block, repeat the above steps.

Once you have measured the volume in cubic centimetres using any of the above methods, you can calculate the total energy by multiplying the volume (X cm3) by 3. This calculation will provide you with an estimation of the total energy transferred during the penetration.

Additional Analysis

Blood Stain Pattern Analysis (BPA): BPA is a distinct area of science that is used to interpret blood stains within forensics. Understanding how analysts interpret bloodstains requires a foundational knowledge of blood's basic properties. Blood consists of both liquid elements (plasma and serum) and solid components (red blood cells, white blood cells, platelets, and proteins). While blood is in a liquid form within the body, once it exits, it remains in a liquid state temporarily. However, except for individuals with hemophilia, blood begins to clot shortly after leaving the body, creating a dark, glossy gel-like substance that solidifies over time. The presence of blood clots in bloodstains can indicate that the attack was prolonged or that the victim continued to bleed for an extended period post-injury.

The manner in which blood exits the body can vary based on the type of injury sustained. It may flow, drip, spray, spurt, gush, or ooze from wounds.

There are three main categories of blood stain, however in terminal ballistics the primary we encounter is gunshot spatter. Gunshot spatter encompasses both forward spatter originating from the exit wound (if the projectile passes through the body) and back spatter from the entrance wound. The characteristics of gunshot spatter can differ based on factors such as the gun caliber, the location of the victim's injury, whether the bullet exits the body, the distance between the victim and the firearm, and the victim's position in relation to walls, floors, and objects. Generally, forward spatter presents as a fine mist, while back spatter consists of larger and fewer drops.

Using Ballistic Sims we can recreate scenarios to replicate crime scenes using different weapons. comparisons can then be carried out along with measurements of the distance gunshot spatter has been projected.

Below is a basic guide on analysing spatter.

Assess the bloodstain patterns: Examine the bloodstains left at the crime scene, focusing on the location, size, shape, and distribution of the spatter. Different patterns may indicate different distances. A more dense spatter pattern can indicate a closer proximity or higher velocity projectile. There are various types of blood spatter, including high-velocity spatter, medium-velocity spatter, and low-velocity spatter.

Examine the size and shape of blood droplets: Typically, as the distance between the shooter and the victim increases, the size of the blood droplets decreases. This is due to the loss of velocity and energy during flight. Round and uniform drops against a wall generally indicate a lower velocity for the spatter itself. A drop with ‘feathering’ around the edges generally indicates higher velocity spatter.

Analyse the impact angle: The angle at which the blood droplets strike a surface can provide additional information about the distance. When the angle is more perpendicular to the surface, it suggests a closer distance, while a shallower angle indicates a greater distance.

Consider the overall spatter pattern: The overall pattern of the bloodstains, including their distribution and concentration, can give insights into the shooter's proximity to the victim. For example, a concentrated cluster of spatter may suggest a close-range shot.

Compare with known reference samples: To enhance accuracy, it is important to have reference samples from known distances. This can be achieved by recreating the shooting scenario under controlled conditions.

Bone Hydraulics: Bone hydraulics is the effect of an impact from a projectile on the ‘long bones’ of the body. These include but are not limited to the femur, tibia and fibular. On impact these ‘long bones’ experience high internal hydraulic pressures within the marrow medullary cavity. This causes fractures above and below the impact point that are often larger than the width of the projectile and permanent wound cavity but within the temporary wound cavity region. This understanding the temporary and permanent cavities along with the use of bone inserts within Ballistic Gel allows you to forecast the damage to a bone (especially within limbs). Conversely, the damage to a long bone and the range of fractures can help indicate velocity of a projectile.

Further Information

If you would like additional assistance on analysis, please feel free to contact the team.