What is Forensic Ballistics?
Forensic ballistic is the examination of evidence relating to firearms at a crime scene, which studies ballistic speed, mobility, angular movement, and the effects of projectile units, such as; bullets, missiles, and bombs.
Who is a Father of Forensic Ballistics?
Calvin Hooker Goddard is known as a father of forensic ballistic.
He was a forensic scientist, army officer, academic, researcher and a pioneer in forensic ballistics.
What Can Ballistics Determine?
Forensic ballistic determines :-
- Which type of gun uses by the criminal?
- Whether the gun is associated with any other crime?
- The amount of damage a bullet can inflict.
- Estimate the position of shooter by analyzing the bullet marks.
- From which angle the gun was fired?
- When the gun was fired?
- The type of impact made by bullet.
- To reveal the shooter’s identity.
- Comparison of different firearm, bullets, and, cartridge cases.
A forensic ballistics expert is who matches, analyzes and examines bullets, cartridges, fragments, and other evidence with the weapons of alleged suspects or others involved in a case.
The first case of forensic firearm examination
The first case of forensic firearm examination was done and documented in 1835. That was when Henry Herbert Goddard applied ballistic fingerprinting to link a bullet recovered from the victim to the actual culprit. After careful inspection of bullet he found that there was a deformation on the surface of the slug that was not because of barrel or by the impact. It appeared as a manufacturing defect. He understood that retrieving the shot form the weapon would help him easily confirm the shooter. When the suspect’s house was checked, a mold was found at his house. the marks on the mold and the mark on the bullet matched completely after comparison. Finally he confessed his crime.
Basic Theory Of Firearm Mechanism
The weapon aims to convert chemical energy into kinetic energy in order to expel a projectile from the firearm.
The Mechanism is :
A round consists of an outer cartridge case, a bullet, some form of propellant, and a percussion cap is first loaded and locked into the breach.
The firing pin is generally mechanically restrained and, when the firearm is cocked, the firing pin spring is compressed.
As the trigger is pulled, the hammer-mounted firing pin is forced forward to strike through a small hole in the breech face, hitting the primer cup (contains a mixture of sensitive chemicals), which rapidly burn and produce sufficient hot gases to ignite the propellant.
As the gunpowder is ignited an expansion of gas occurs which, confined in a small space, eventually forces the bullet down the barrel of the firearm.
Types Of Ballistics
Internal Ballistics – Internal ballistic is about Motion of the projectile in the bore of the weapon.
External Ballistics – External Ballistic is about Motion of the projectile from muzzle end of the barrel to the target.
Terminal Ballistics– Terminal Ballistics also known as Wound Ballistics. It deals with the effect of projectile on the target.
Transitional Ballistics– It deals with the motion of the projectile from the time it leaves the muzzle until the pressure behind the projectile is equalized.
Types of Firearm
Revolver – Revolver is a Handgun that has a cylinder with holes to contain the cartridges. The cylinder revolves to bring the cartridge into position to be fired.
Rifle – Essentially a long rifled barrel firearm primarily designed for relatively long range use in warfare or hunting. Rifles are available as single shot, self-loading, manual action, bolt action or automatic, though most commonly encountered are self-loading.
Submachine Gun – A fast-loading weapon with a high rate of fire, available as single shot or fully automatic. The inaccurate SMG is a magazine-fed weapon which can hold up to around 100 rounds, designed for continuous fire.
Machine Gun – A machine gun is a fully-automatic firearm. This has a very high rate of fire with a fast reload time and great power. They are generally only used by the military.
Shotgun – A shoulder-fired long gun with no rifling in the barrel, designed to shoot a large number of small projectiles (“shot”) rather than a single large projectile (“a bullet”).
Pistols – Pistols are firearms designed for a more automatic operation. Cartridges are loaded into an ammunition magazine which is inserted into the firearm.
Other – Other types include:
- Air Guns,
- Gas Guns,
- Antique Guns,
- Light Weapons, Etc.
Examination Of Bullets
The make and model of the weapon can also be inferred from the combination of different class characteristics that are common to specific manufactures. The three main class characteristics of all bullets are the :
- Lands And Grooves,
- The Caliber Of The Bullet,
- And The Rifling Twist.
Lands are the raised portions between the grooves inside the barrel after the spiral grooves are cut to produce the rifling.
In firearms, caliber is the specified nominal internal diameter of the barrel.
Rifling twist refers to the rifling in the barrel of modern rifles making a full 360 degree rotation in a given length of inches.
These random imperfections or irregularities can be produced by:
- Wear from Abuse
- Wear from Use
The striations on the bullet can make identifiable and unique markings that trace it back to a particular firearm.
How Good a Match is It?
The theory behind firearm identification is that microscopic striations and impressions left on bullets and cartridge cases are unique, reproducible, and therefore, like “ballistic fingerprints” that can be used to identify a gun. If investigators recover bullets or cartridge cases from a crime scene, forensic examiners can test-fire a suspect’s gun to see if it produces ballistic fingerprints that match the evidence.
Ballistic Fingerprinting – Ballistic fingerprinting refers to a set of forensic techniques that rely on marks that firearms leave on bullets to match a bullet to the gun it was fired with.
The comparison microscope is a most important tool for firearm examination.
Two bullets can be observed and compared at the same time within the same field of view.