Chapter 9: Firearms, Tool Marks, and Other Impressions

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Handguns, Long

Firearms can be divided into two categories: _________ and ________ guns.

Single-shot, Revolvers, Semiautomatics

Handguns, or pistols, are firearms that are designed to be held and fired with one hand, and the most common types of handguns are ________, ________, and ________.

Revolver

The ________ features several firing chambers, each holding one cartridge, located within a revolving cylinder that lines the chamber up with the barrel mechanically when the round is fired.

Shot

A cartridge for a shotgun, called a shell, contains numerous ball-shaped projectiles, called ________.

Choke

A shotgun barrel is not rifled and can also be narrowed toward the muzzle in order to concentrate shot when fired. The degree of narrowing of the barrel is called the ________ of the shotgun.

Land

The ________ is the original part of the bore left after rifling grooves are formed.

Caliber

The diameter of the gun barrel is known as its _________.

True

True or False: The number of lands and grooves is a class characteristic of a barrel.

Individual

The _________ characteristics of a rifled barrel are formed by striations impressed into the barrel's surface.

Comparison Microscope

The most important instrument for comparing bullets is the ___________.

Striations

To make a match between a test bullet and a recovered bullet, the lands and grooves of the test and evidence bullet must have identical widths, and the longitudinal _________ on each must coincide.

False

True or False: It is always possible to determine the make of a weapon by examining a bullet it fired.

Smooth

A shotgun has a _________ barrel.

Gauge

The diameter of a shotgun barrel is expressed by the term _________.

False

True or False: Shotgun pellets can be individualized to a single weapon.

True

True or False: A cartridge case can be individualized to a single weapon.

NIBIN

The automated firearms search system developed by the FBI and ATF as a unified system incorporating both DRUGFIRE and IBIS technologies is known as ________.

True

True or False: The distribution of gunpowder particles and other discharge residues around a bullet hole permits an approximate determination of the distance from which the gun was fired.

False

True or False: Without the benefit of a weapon, an examiner can make an exact determination of firing distance.

12, 18

A halo of vaporous lead deposited around a bullet hole normally indicates a discharge ___ to ___ inches from the target.

Bullet Wipe

If a firearm has been fired more than 3 feet from a target, usually no residue is deposited, but a dark ring, known as ________, is observed.

Yard

As a rule of thumb, the spread in the pattern made by a 12-gauge shotgun increases 1 inch for every _______ of distance from the target.

Infrared

An _________ photograph may help visualize gunpowder deposits around a target.

True

True or False: One test method for locating powder residues involves transferring particles embedded on the target surface to chemically treated photographic paper.

Primer

Current methods for identifying a shooter rely on the detection of ________ residues on the hands.

Barium, Antimony

Determining whether an individual has fired a weapon is done by measuring the elements ________ and ________ present on the hands.

False

True or False: Firings with all types of ammunition can be detected from hand swabbings with nitric acid.

Scanning Electron Microscope (SEM)

Microscopic primer and gunpowder particles on the adhesives applied to a suspected shooter's hand can be detected with a ___________.

True

True or False: Restoration of serial numbers is possible because in the stamped zone the metal is placed under a permanent strain the extends beneath the original numbers.

False

True or False: It is proper to insert a pencil into the barrel when picking up a crime-scene gun.

Base, Nose

Recovered bullets are initialed on either the _______ or ________ of the bullet.

False

True or False: Because minute traces of evidence such as paint and fibers may be adhering to a recovered bullet, the investigator must take care to remove these trace materials immediately.

False

True or False: Cartridge casings are best marked at the base of the shell.

Gunpowder Residue

The clothing of the victim of a shooting must be handled so to prevent disruption of ________ around bullet holes.

Tool Mark

A _________ is any impression caused by a tool coming into contact with another object.

Striations

Tool marks compare only when a sufficient number of _________ match between the evidence and test markings.

Cast

Objects bearing tool marks either should be submitted intact to the crime lab, or a ________ should be taken of the tool mark.

Electrostatic Lifting Device

An imprint may be lifted using lifting sheets or an __________.

Photography, Casting

Shoe and tire marks impressed into soft earth at a crime scene are best preserved by ________ and ________.

Individual

A wear pattern, cut, gouge, or other damage pattern can impart ________ characteristics to a shoe.

Bore

The interior of a firearm.

Grooves

The cut or low-lying portions between the lands in a rifled bore.

Rifling

The spiral grooves formed in the bore of a firearm barrel that impart spin to the projectile when it is fired.

Lands

The raised portion between the grooves in a rifled bore.

Caliber

The diameter of the bore of a rifled firearm, usually expressed in hundredths of an inch or millimeters--for example, .22 caliber and 9 millimeter.

Breech Face Mark

The rear part of a firearm barrel.

Gauge

The size designation of a shotgun; originally the number of lead balls with the same diameter as the barrel that would make a pound. The only exception is the .410 shotgun, in which bore size is .41 inch.

Choke

An interior constriction placed at or near the muzzle end of a shotgun's barrel to control shot dispersion.

Distance Determination

The process of determining the distance between the firearm and a target, usually based on the distribution of powder patterns or the spread of a shot pattern.

Extractor

The mechanism in a firearm that withdraws a cartridge or fired case from the chamber.

Ejector

The mechanism in a firearm that throws the cartridge or fired case from the firearm.

Firearms Identification

A discipline primarily concerned with determining whether a bullet or cartridge was fired by a particular weapon.

Greiss Test

A chemical test used to examine patterns of gunpowder residues around bullet holes.

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