Untitled Quiz

Firearm and Toolmark Identification

• Forensic ballistics examines evidence from firearms used in a crime.
• When a bullet is fired, microscopic marks (ballistic fingerprints) are left on the bullet and cartridge case.
• Forensic examiners test-fire a suspect's gun to compare marks with those from the crime scene.
• This comparison determines if the bullets likely came from the same gun or different guns.
• Cartridge cases are compared similarly.

Terms and Definitions

• Field Test: Testing a firearm's operating condition without ammunition.
• Function Test: Examining a firearm’s mechanical condition and operation to ensure safety features are operable and ability to fire a cartridge.

Test Fire

• Test firing a firearm in a controlled laboratory setting to obtain representative bullets and cartridge cases for comparison.
• This is done to determine the functionality of the firearm.

Physical Examination

• Describing the firearm, including make, manufacturer, type (shotgun, rifle, pistol, revolver), model, caliber/gauge, and serial number.
• Inspecting the bore(s), rifling type (e.g., polygonal or conventional), number of lands and grooves, and direction of rifling twist.

Examination of Suspected Weapon

• Examination of Criminal Bullet: Assessing the caliber, marks (number, diameters, and width of lands or grooves), depth of grooves, and direction of grooves.
• Examination of Criminal Empty Cartridge Case: Analyzing marks on the case, specifically the firing pin (concentric or eccentric).

Firing test of suspected weapon

• Using a comparative microscope for a detailed examination of the suspected weapon.

Examination of Chemical Residues in Barrel

• Used to detect the crime weapon or time of firing.

Firearms Identification

• Focuses on determining if a bullet or cartridge was fired from a specific weapon.
• It is distinct from ballistics, which studies projectile motion.

Bullet Comparison

• The barrel of a gun marks bullets uniquely, enabling comparison with test-fired bullets to determine origin.

Rifling in Firearms

• Rifle barrels have spiral grooves (rifling) that impart spin to bullets.
• These grooves and their characteristics (e.g., number, width, direction of twist, depth) are unique to each barrel, and thus each gun.
• There are no two identical striation markings between rifled barrels

Comparing Bullets and Cartridge Cases

• Examining a bullet's class characteristics (e.g., the number of lands and grooves, the direction of twist) and class characteristics of the firearm, including the shape of the firing pin.
• The method of comparing markings uses microscopes.

Shotguns in terms of Striations

• Shotguns have smooth barrels; therefore, there are no grooves for the bullets to interact, so no striations are made on the bullet, and they are identified solely through their bullet gauge.

Cartridge Case Comparison

• Pulling the trigger in a firearm releases the firing pin to strike the primer, igniting gunpowder.
• Expanding gases propel the bullet and simultaneously push the spent cartridge case or shell back.
• The cartridge case is marked by contact with the weapon's firing and loading mechanisms.

Types of Firearms

• Revolver, Pistol, Rifle, and Shotgun.
• Descriptions and images are provided in other sections.

Types of Cartridges /Ammunition:

• The different cartridges are associated to the different firearms as well as their various types (e.g. Rimless or Rim type bullets)

Medico legal Importance of Lead Shot or Pellets

• Type of weapon recognition.
• Determining the firing distance.

Wads (external and internal)

• Descriptions and types of wads like internal and external.

Examination of Chemical Residues

• Gunshot residue (GSR) is composed of burnt and unburnt particles from the primer and gunpowder and vaporized lead.
• GSR detection techniques, such as the Griess test, lead residue test, and diphenylalamine test, are used to determine the presence and characteristics of GSR.

Chemical residues and Tests

• Griess Test: Detects nitrite residues, a by-product of smokeless gunpowder combustion. Determines muzzle-to-garment distance.

• Sodium Rhodizonate Test: Detects lead residues. Pink color indicates the presence of lead; a dark blue color confirms the presence.

Conducting the Examination

• Cases and bullets are compared using a special comparison microscope.

Questions and Answers

• The provided documents include questions on firearms identification, chemical residue analysis, and different types of firearms (revolver, pistol, shotgun, rifle).