What is ballistics? Give 3 examples of how ballistics is used in forensic science.

Forensic Science: Fundamentals & Investigations, Chapter 17 Introduction Ballistic evidence helps explain: What type of firearm was used. The caliber of the bullet. The number of bullets fired. Where the shooter was. Whether a weapon was fired recently. If a firearm was used in previous crimes. Forensic Science: Fundamentals & Investigations, Chapter 17

History of Forensic Firearm Identification 1835 – London, England. Mold mark used to make bullet from molten lead used as evidence in homicide case 1863 – Examination of the bullet type and design used to shoot Gen. Stonewall Jackson showed he was shot by one of his own men 1879 – Minnesota. Rifling marks from a revolver used in court to differentiate two revolvers 1925 – The comparison microscope is developed by Philip Gravelle Please refer to the document titled “History of Firearm Identification” by Dr. James Hamby included on the disk for more information and discussion topics.

Firearm Nomenclature Slide Barrel Extractor Trigger Hammer Safety We first need to discuss the various parts of a firearm to understand the functioning of a firearm. The slide of a semiautomatic firearm is used to load the firearm. In order to fire a semiautomatic pistol, the ammunition is loaded in a magazine and placed in the grip. The slide is then pulled to the rear under spring tension. On its’ forward return the slide strips a cartridge from the magazine into the barrel of the firearm. The firearm is now ready to fire.

Ammunition bsapp.com

Caliber of the Cartridge Caliber is a measure the diameter of the cartridge in hundredths of an inch. Common calibers include .22, .25, .357, .38, .44, and .45. Why should the caliber of ammunition match the firearm that shoots it? If they do not match, what could go wrong? If they don’t match – the bullet could get stuck or possibly cause the gun to explode/get extremely hot/backfire. Forensic Science: Fundamentals & Investigations, Chapter 17

Forensic Science: Fundamentals & Investigations, Chapter 17 Bore Interior diameter of a gun barrel Forensic Science: Fundamentals & Investigations, Chapter 17

Bullets, Cartridges, and Calibers Bullets and cartridges are packaged together. The bullet, usually of metal, is out front with the cartridge, holding the primer and propellant powders, behind. Forensic Science: Fundamentals & Investigations, Chapter 17

Forensic Science: Fundamentals & Investigations, Chapter 17 Shotgun Ammunition Gauge- interior diameter of a shotgun barrel as determined by the number of lead balls of a size fitting in the barrel Shot- lead spheres in a shotgun shell Slug- single pellet or sphere Forensic Science: Fundamentals & Investigations, Chapter 17

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Bullet Design “Bullet” refers to the projectile(s) which actually exits the barrel of the gun when fired Bullets vary in shape and composition There exist hundreds of different types of bullets Most types are variations on three main shapes & three basic compositions bsapp.com

Three Main Shapes bsapp.com

Round Nose Maximum penetration Cheapest shape to manufacture Easily loads into chambers bsapp.com

Hollow Point Spreads or mushrooms on impact Causes additional damage to target Inhibits penetration bsapp.com

Wad Cutter Used exclusively as a practice load Minimizes penetration Rips a hole in target paper which is visible by the shooter bsapp.com

Three Basic Compositions of Bullets Lead ½ Jacketed Jacketed (Full metal jacket) bsapp.com

Lead Cheap Dense Soft Easy to mold bsapp.com

½ Jacketed A lead bullet coated with copper half way up the exposed portion of the bullet Used primarily for hollow points Copper improves exit velocity Lead promotes mushrooming bsapp.com

Jacketed A lead bullet completely coated in copper Copper improves exit velocity Used to hold the shape of the bullet in an effort to maximize penetration bsapp.com

What happens to bullets when they are fired? bsapp.com

Pull the Trigger and . . . A pin or hammer strikes the primer. This causes a spark. The powder is then ignited causing an explosion. This explosion starts the bullet down the barrel of the gun bsapp.com

Down the Barrel As a bullet travels down the barrel of a gun it is twisted by the lands and grooves of the barrel. bsapp.com

Out of the Barrel 5.This rifling causes the bullet to exit the end of the barrel in a spiral motion. http://www.youtube.com/watch?v=lVgTTAukMOU bsapp.com

Bullet Analysis & Comparison What are some characteristics used to identify & compare bullets? bsapp.com

Striations bsapp.com

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Forensic Science: Fundamentals & Investigations, Chapter 17 Striae/cannelures Parallel sets of scratches on a bullet caused by unique markings in the bore of a rifled weapon (like fingerprint) Can be hard to see if badly deformed pg. 445 Cannelures- groves on bullet that help secure it to the cartridge casing Forensic Science: Fundamentals & Investigations, Chapter 17

Forensic Science: Fundamentals & Investigations, Chapter 17 Cartridge Consists of bullet and case (with powder) Can be both class & individual evidence Head stamp- numbers or letters found at base of cartridge (show caliber, code & manufacturer) Forensic Science: Fundamentals & Investigations, Chapter 17

Breech Marks Portion of gun that contains firing mechanism Can have marks on them after cartridge is slammed backward after being fired bsapp.com

What happens to the cartridge after firing the firearm? Extractor- hooked type part that withdraws the casing from the chamber after firing Ejector- part that throws out casing after gun is fired Forensic Science: Fundamentals & Investigations, Chapter 17

Some scratches may not be from firing Can happen because of movement before firing Can happen in magazine or chamber Magazine (clip)- container that holds cartridges under pressure to be fed into chamber Chamber- holds cartridge for firing Forensic Science: Fundamentals & Investigations, Chapter 17

Forensic Science: Fundamentals & Investigations, Chapter 17 Review Modern ammunition consists of what four many parts? Explain how bullet are sized differently in handguns and rifles as opposed to shotguns? What are the three main bullet types? What is on the back of the cartridge that shoes the manufacturer, caliber, & size? What part of an unfired bullet helps to keep the cartridge case attached to the bullet? Why do you think breech marks are important to forensics? Forensic Science: Fundamentals & Investigations, Chapter 17

Comparison Microscope Two scopes- One Field bsapp.com

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What happens to a bullet when it hits a target? Most bullets tend to mushroom when they hit a target. Some bullets nearly disintegrate. Left are bullet fragments from a ½ jacketed hollow point. bsapp.com

Not all bullets mushroom the same Not all bullets mushroom the same. A lot depends on the speed and shape of the bullet, and the characteristics of the target. bsapp.com

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Some more bullets recovered after firing The striations from the rifling are still visible bsapp.com

Forensic Science: Fundamentals & Investigations, Chapter 17 Gunshot Residues Chemical testing often can detect gun shot residue even if removal is attempted. What does this mean for investigation? Forensic Science: Fundamentals & Investigations, Chapter 17

Forensic Science: Fundamentals & Investigations, Chapter 17 Databases Like fingerprints, there is a federal database for firearms used in previous crimes – NIBIN (National Integrated Ballistics Network). Forensic Science: Fundamentals & Investigations, Chapter 17