Forensic sci Flashcards
ballistics
How is ballistics defined?
Ballistics is the study of the motion, behavior, and effects of projectiles, particularly bullets, from the moment of discharge until they hit their target.
What can ballistics tell investigators?
Ballistics can help investigators determine the type of weapon used, the trajectory of a bullet, the distance from which it was fired, and whether the weapon has been previously used in other crimes.
How do handguns and long guns differ?
Handguns are smaller firearms designed to be operated with one hand, while long guns (like rifles and shotguns) are larger and designed to be fired from the shoulder.
What is the difference between a cartridge and a shot shell?
A cartridge is a complete unit of ammunition for a firearm, containing a bullet, powder, and primer. A shot shell is a type of cartridge used in shotguns, typically containing multiple pellets (shot) instead of a single bullet.
What are the parts of a cartridge?
The parts of a cartridge include the bullet (projectile), casing (shell), powder, and primer.
What is a caliber? With what types of firearms is it associated?
Caliber is the diameter of the barrel and the bullet, often measured in millimeters or inches. It is associated with handguns and rifles.
What is a gauge? With what type of firearm is it associated?
A gauge is a measurement used for shotguns, indicating the size of the bore (the internal diameter of the barrel). It is inversely related to the number of lead balls of the gauge size that can be made from one pound of lead.
How does one measure the caliber of a bullet?
Caliber is measured by the diameter of the bullet, either in millimeters or inches, and is usually labeled on the cartridge.
What method do investigators use to test-fire comparison bullets?
Investigators use a test-firing technique with a firearm in a controlled setting, often into a water tank or ballistic gel, to compare the markings on test bullets with those found at crime scenes.
When unique markings are found on a bullet or cartridge, from what sources might those markings originate?
Markings on bullets or cartridges might come from the firearm’s rifling, firing pin, extractor, ejector, or other parts of the firearm that come into contact with the ammunition.
What is a striation?
A striation is a microscopic marking left on a bullet by the rifling inside the barrel of a firearm, which can be used to match a bullet to a specific weapon.
What are firing pin markings?
Firing pin markings are impressions left on the primer of a cartridge when the firing pin strikes it, which can help identify the firearm used to discharge the round.
What are extractor marks?
Extractor marks are scratches or impressions left on a cartridge case when the firearm’s extractor pulls the case from the chamber.
What are ejector marks?
Ejector marks are marks left on a cartridge case when the firearm’s ejector expels the case from the chamber.
What is gunshot residue and what does it tell investigators?
Gunshot residue (GSR) consists of tiny particles from the primer and powder of a discharged firearm. Its presence on a person’s hands or clothing can suggest that they have recently fired a weapon.
What are internal ballistics?
Internal ballistics refers to the processes that occur inside the firearm, from the moment the trigger is pulled until the bullet exits the barrel.
What are external ballistics?
External ballistics studies the behavior of the bullet once it leaves the barrel, including its trajectory, velocity, and the effects of air resistance and gravity.
What are terminal ballistics?
Terminal ballistics focuses on the effects of a projectile when it strikes its target, including penetration, expansion, and damage caused to the target.
How does an investigator calculate a bullet’s trajectory?
Investigators calculate a bullet’s trajectory by analyzing the bullet’s entry and exit wounds, the angle of the firearm, and the bullet’s velocity, often using specialized software and physics principles.
What is bullet wipe?
Bullet wipe is the dark ring or residue left around a bullet’s entrance hole, created by the oils and dirt on the bullet’s surface when it contacts a target.
How do you calculate a bullet’s point of origin?
To calculate a bullet’s point of origin, investigators analyze the trajectory of the bullet from multiple entry or exit points, using angles and distances to pinpoint where the bullet was fired.
What does the term trajectory mean?
Trajectory refers to the path a bullet follows from the firearm to its target, influenced by factors like speed, angle, and external forces such as gravity and air resistance.
What is the name of the database that holds ballistics information?
The National Integrated Ballistic Information Network (NIBIN) is a database that holds ballistics information, including images of fired cartridge cases and bullets.
