Question The inner surface of the barrel of a gun leaves its markings on a bullet passing through...
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Transcript of Question The inner surface of the barrel of a gun leaves its markings on a bullet passing through...
QuestionThe inner surface of the barrel of a gun
leaves its markings on a bullet passing through it. These markings are peculiar to each gun. Would these markings be considered class characteristics or individual characteristics?
AnswerBoth. The lands, grooves and twists are
class evidence while the microscopic striations are considered individual evidence.
QuestionWhat is the purpose of rifling, or impressing
the inner surface of a barrel of a gun with spiral grooves?
AnswerThe grooves serve to guide a fired bullet
through the barrel, imparting a rapid spin to insure accuracy and optimum distance.
QuestionThe surfaces of the original bore
remaining between the grooves are called __________.
AnswerLands
QuestionThe diameter of the gun barrel,
measured between opposite lands, is known as _____.
Answercaliber
QuestionTrue or False?Once a manufacturer chooses a rifling
process, the class characteristics of the weapon’s barrel will remain consistent, each will have the same number of lands and grooves, with the same approximate width and direction of twist.
AnswerTrue
QuestionTrue or False?No two rifled barrels, even those
manufactured in succession, will have identical striation markings.
AnswerTrue
QuestionThe single most important tool to a
firearms examiner is the ____________.
AnswerComparison Microscope
QuestionUnlike rifled firearms, a shotgun has a____________ barrel.
Answersmooth
QuestionThe diameter of the shotgun barrel is
expressed by the term _________. The ________ this number is, the _________ the barrel’s diameter.
AnswersGaugeHighersmaller
QuestionThe shape of the _______________will be
impressed into the relatively soft metal of the primer on the cartridge case.
AnswerFiring pin
QuestionThe cartridge case, in its rearward
thrust, is impressed with the surface markings of the _________________.
Answersbreechblock
QuestionWhat do you call the rear part of a firearm
barrel?
AnswerThe Breechblock
QuestionThe interior of a firearm barrel.
AnswerBore
QuestionThe cut or low-lying portions between the
lands in a rifled bore.
AnswerGrooves
QuestionThe spiral grooves formed in the bore of a
firearm barrel that impart spin to the projectile when it is fired.
AnswerRifling
QuestionFactors such as barrel length, caliber, type of
ammunition, and type and condition of the weapon fired influence the amount of gunpowder residue deposited on a target. True or False?
AnswerTrue
QuestionDistinctive markings that may appear on
the shell as a result of metal to metal contact can be caused by the _____________which is the mechanism in a firearm that throws the cartridge or fired case from the firearm.
AnswerEjector
QuestionDistinctive markings that may appear on
the shell as a result of metal to metal contact can be caused by the __________which is the mechanism in a firearm by which a cartridge of a fired case is withdrawn from the firing chamber.
AnswerExtractor
QuestionDistinctive markings that may appear on
the shell as a result of metal to metal contact can be caused by the __________which is the mechanism that in a firearm holds the bullets.
AnswerMagazine or clip
QuestionThese are fine lines found in the interior
of the barrel. They are impressed into the metal as the negatives of minute imperfections found on the rifling cutter’s surface, or they are produced by minute chips of steel pushed against the barrel’s inner surface by a moving broach cutter.
AnswerStriations
Questions
During the initial phase of comparison between an evidence bullet and a test-fired bullet, what characteristics are often looked at first?
AnswerClass characteristics such as grooves, lands
and twists.
QuestionNot only must the lands and ___________ of
the test and evidence bullet have identical widths, but the ____________________ striations on each must coincide.
AnswerGrooves,Longitudinal
QuestionThe NIBIN was eliminated the need for
forensic ballistic specialists. True or False?
AnswerFalse - the ultimate decision for making a
final bullet comparison will be determined by the forensic examiner through traditional microscopic methods.
QuestionThis network produces database files
frombullets and cartridge casings retrieved
fromcrime scenes or test fires from retrieved
firearms, often linking a specific weapon to multiple crimes.
AnswerThe National Integrated Ballistics
InformationNetwork, NIBIN
QuestionA star-shaped (stellate) tear pattern
around the bullet hole entrance, surrounded by a rim of a smokeless deposit of vaporous lead usually indicates a weapon discharge of ________________ from the target.
AnswerOf less than one inch
QuestionA halo of vaporous lead (smoke)
deposited around a bullet hole is normally indicative of a discharge of ______________or less.
Answer12 to 18 inches
QuestionThe presence of scattered specks of
unburned and partially burned powder grains without any accompanying soot is normally indicative of a discharge observed at distances ________________.
Answerup to 25 inches (and occasionally as far
as 36 inches).
QuestionDischarges that occur more than three
feet from the target will usually not deposit any powder residues, and the only visual indication is a dark ring around the hole, known as a __________________.
AnswerBullet wipe
QuestionWhat is the test used to detect gunpowder
residues that are not visible?
AnswerGreiss Test
QuestionRestoration of serial numbers is possible
through ____________________because the metal crystals in the stamped zone are placed under a permanent strain that extends a short distance beneath the original numbers.
chemical etching
QuestionWhen shoe and tire marks are impressed
into soft earth at a crime scene, their preservation is best accomplished by ___________ and _______________.
AnswerPhotography and casting
QuestionA sufficient number of _________________or
the uniqueness of such points will support a finding that both the questioned and test impressions originated from one and only one source.
Answerpoints of comparison
QuestionThe scene investigator should attempt to
fit the suspect tool into the tool mark in order to make sure the correct tool is being sent to the crime lab.
AnswerFalse, Any contact between the tool and
the marked surface may alter the mark and will, at the least, raise serious questions about the integrity of the evidence.
QuestionA _________________is considered to be any
impression, cut, gouge, or abrasion caused by a tool coming into contact with another object.
Answertool mark
QuestionA careful examination of the impression
can reveal important class characteristics, such as the _______________________________ of the tool.
Answer
the size and shape
QuestionIt is the presence of any minute
imperfections on a tool that imparts _______________to that tool.
Answerindividuality
QuestionA forensic _________________may conclude that
a bite mark was made by a particular individual if a sufficient number of points of similarity between test and suspect marks are present.
Answerodontologist
QuestionName a projectile that is not expected to
show any evidential marks or impressions.
AnswerA shotgun pellet
QuestionTrue or False?In collecting and packaging firearms
evidence at a crime scene, an investigator must mark a fired bullet on its base for identification.
AnswerTrue
QuestionTrue or False?In collecting and packaging firearms
evidence at a crime scene, an investigator must avoid inserting a stick or pencil into the barrel of a weapon.
AnswerTrue
QuestionTrue or False?In collecting and packaging firearms
evidence at a crime scene, an investigator must mark an empty bullet on its base for identification.
AnswerFalse
QUESTIONTrue or False?In collecting and packaging firearms
evidence at a crime scene, an investigator must unload a weapon before shipping it to the crime laboratory.
AnswerTrue
QuestionIdentify the two elements detected on the
hands of an individual who has recently fired a bullet are:
AnswerBarium and Antimony