Forensic Insight: Unraveling Firearm Ballistics, Footwear Evidence, and Blood Spatter Interpretation

Published: 2024-01-23
Forensic Insight: Unraveling Firearm Ballistics, Footwear Evidence, and Blood Spatter Interpretation
Type of paper:  Essay
Categories:  Analysis Forensic science
Pages: 5
Wordcount: 1175 words
10 min read

Define a firearm

A firearm is any weapon that is designed to shoot a projectile by explosive action. This reaction is made possible by the chemical reaction of gunpowder. The legal definition from NJ states that "firearms are any handguns, rifles, shotguns; machineguns assault firearms, automatic or semi-automatic rifles or any guns, device or instruments like a weapon. Now from this weapon, a solid projectile, ball, slug, pellet, missile, bullet, gas, or any vapour may be fired using a cartridge or shell. It is fired by the action of an explosive or the igniting of flammable substances.

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What is the difference between firearms evidence and ballistics?

The term firearms evidence refers to examining evidence that includes tool marks in the form of bullet striation, pattern in the form of burn marks, blood spatter and fingerprints on the firearm. Ballistics evidence, on the other hand, determines a bullet's trajectory by measuring the distance that is travelled by the shot and the emanating area where this bullet was located.

What are the divisions of ballistics evidence?

Ballistic evidence is divided into four sections, internal evidence, transitional evidence, external evidence, and terminal evidence. Internal evidence has to do with what happens inside the firearm. Transitional evidence explains the process of the bullet exiting the barrel of the gun and the striations it leaves behind. Then external evidence deals with the trajectory the shell takes as it leaves the weapon and travels to the target. Finally, terminal evidence is evidence that shows the impact of the bullet on the target.

What are the individualizing characteristics?

Individual characteristics are the traits that make a bullet unique to the firearm that it was shot from. These characteristics can be produced randomly from tools used to manufacture the surface of the bullet's land and grooves' surface.

How does glass fracture?

Glass fractures when an object strikes it. The item will often create a ridge that is called a conchoidal fracture. These fractures are parallel to the side where an object's force was applied to the glass.

How does beveling determine the direction and angle of a bullet through the glass and bone?

Beveling can be used to determine the direction by analyzing the side of the cone-shaped hole that is formed by a bullet. The small hole in the glass is usually at the entry point of the shot, and the larger hole is on the exit side.

Fractures can help a great deal in determining the sequence of bullets, and the impact they have on the glass, such as a radial fracture. It begins at the bullet hole and flows outward. Concentric fractures are formed in a circular pattern around the impact point. These specific fractures do not interfere with each other; they stop when they converge with another fracture. The sequence of bullet holes can be determined by analyzing radial fractures.

How is footwear evidence collected and compared? What are the different methods of lifting footwear impressions?

Footwear evidence is a classic piece of evidence left at crime scenes. Footwear impressions can be classified into three categories: the visible print (patent), the invisible print (latent) and the plastic print (3-dimensional). The footwear evidence collected from the crime scene depends on its classification. The visible patterns can be seen by the naked eye and do not require any form of aid to be developed. They can be collected by taking photographs.

The invisible prints are similar to fingerprints at a crime scene and are developed the same way. There is a need for treatment to collect these from a crime scene. The experts often use powder, chemical enhancement and different types of forensic light sources. The prints are also photographed as standard procedure in the recovery process. Plastic impressions are formed on soft surfaces such as much, snow and wet sand. These impressions must be photographed before any other procedure can take place. The systems include casting, lifting and Bio-foam methods.

After the collection of footwear impressions, the examiners are ready to compare the unknown footwear impressions with exemplars using transparent overlays or side-by-side examination.

They use techniques to detect the defects; the methods used are like low magnification. Also, callipers are used to measure the weaknesses and their position to other reference points in a shoe. The arrows are used to indicate the similarity and their corresponding feature on comparison impression. Footwear databases are used to identify the brand style and other shoe features such as SICAR, which help narrow down the field of possible shoes. The examiner's responsibility is to compare the footwear manually and make a source conclusion.

What are the class and individualizing characteristics?

The class characteristics are the characteristics that are made intentionally during the manufacture of a collection of shoes. The features include brand, style, size, gender and the geometrical pattern on the outsole. The individual characteristics are formed by randomly adding or removing something from the original structure of the shoe. These characteristics can include nicks, scratches, cuts, punctures, tears, and air bubbles during manufacture, ragged holes. These unique features can be characterized by length, width, relationship to the shoe perimeter, and other defects. These characteristics position and orientation of defects are marked, measured, and documented.

Describe the goals and process of blood spatter interpretation.

The goal of the interpretation of blood spatter is to recreate the sequence of physical events that caused the blood spatter. The examiners undertake the process of analyzing the blood spatter distribution, and characteristics such as shape, size, volume, and relationship to the crime scene to conclude what happened in the crime scene. Blood spatter analysis makes use of chemistry, biology, and mathematic principles. These scientific principles aid the examiner in reconstructing the actions and help them include or exclude the potential suspect.

The examiner performs the bloodstain pattern analysis in two phases. The first phase is pattern analysis and the reconstruction of the crime scene. For the pattern analysis, the examiner analyzes the physical characteristics of the bloodstains such as distribution, size, location of stain, distance, shape, the surface texture. Then the examiner interprets the pattern of bloodstains and what may cause them. The second phase is the reconstruction of the actions that caused the bloodstains. The examiner uses the angle, direction of the spatter, and the area of origin to estimate where the victim and the perpetrator were positioned when the bloodshed occurred.

How is a blood-spatter documented at the crime scene?

The blood spatters are frequently documented by photographing them from every angle, and a scaler or ruler is placed next to the blood spatter. The scaler is used to provide an accurate measurement. Then, sketches or videos of the crime scene and the blood spatter are taken for analysis and further documentation. The blood spatter collection is not easy to retrieve from the crime scene because some evidence may require removing large objects such as carpets or furniture. Blood spatter evidence should be carefully packaged to protect it from any damage. Collecting blood evidence for DNA profile analysis will be performed by using a swab.

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Forensic Insight: Unraveling Firearm Ballistics, Footwear Evidence, and Blood Spatter Interpretation. (2024, Jan 23). Retrieved from

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