Presentation on theme: "Question The 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."— Presentation transcript:
Question The 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?
Answer Both. The lands, grooves and twists are class evidence while the microscopic striations are considered individual evidence.
Question What is the purpose of rifling, or impressing the inner surface of a barrel of a gun with spiral grooves?
Answer The grooves serve to guide a fired bullet through the barrel, imparting a rapid spin to insure accuracy and optimum distance.
Question The surfaces of the original bore remaining between the grooves are called __________.
Question The diameter of the gun barrel, measured between opposite lands, is known as _____.
Question True or False? Once a manufacturer chooses a rifling process, the class characteristics of the weapons barrel will remain consistent, each will have the same number of lands and grooves, with the same approximate width and direction of twist.
Question True or False? No two rifled barrels, even those manufactured in succession, will have identical striation markings.
Question The single most important tool to a firearms examiner is the ____________.
Answer Comparison Microscope
Question Unlike rifled firearms, a shotgun has a ____________ barrel.
Question The diameter of the shotgun barrel is expressed by the term _________. The ________ this number is, the _________ the barrels diameter.
Answers Gauge Higher smaller
Question The shape of the _______________will be impressed into the relatively soft metal of the primer on the cartridge case.
Answer Firing pin
Question The cartridge case, in its rearward thrust, is impressed with the surface markings of the _________________.
Question What do you call the rear part of a firearm barrel?
Answer The Breechblock
Question The interior of a firearm barrel.
Question The cut or low-lying portions between the lands in a rifled bore.
Question The spiral grooves formed in the bore of a firearm barrel that impart spin to the projectile when it is fired.
Question Factors 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?
Question Distinctive 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.
Question Distinctive 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.
Question Distinctive 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.
Answer Magazine or clip
Question These 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 cutters surface, or they are produced by minute chips of steel pushed against the barrels inner surface by a moving broach cutter.
Questions During the initial phase of comparison between an evidence bullet and a test-fired bullet, what characteristics are often looked at first?
Answer Class characteristics such as grooves, lands and twists.
Question Not only must the lands and ___________ of the test and evidence bullet have identical widths, but the ____________________ striations on each must coincide.
Answer Grooves, Longitudinal
Question The NIBIN was eliminated the need for forensic ballistic specialists. True or False?
Answer False - the ultimate decision for making a final bullet comparison will be determined by the forensic examiner through traditional microscopic methods.
Question This network produces database files from bullets and cartridge casings retrieved from crime scenes or test fires from retrieved firearms, often linking a specific weapon to multiple crimes.
Answer The National Integrated Ballistics Information Network, NIBIN
Question A 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.
Answer Of less than one inch
Question A halo of vaporous lead (smoke) deposited around a bullet hole is normally indicative of a discharge of ______________or less.
Answer 12 to 18 inches
Question The presence of scattered specks of unburned and partially burned powder grains without any accompanying soot is normally indicative of a discharge observed at distances ________________.
Answer up to 25 inches (and occasionally as far as 36 inches).
Question Discharges 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 __________________.
Answer Bullet wipe
Question What is the test used to detect gunpowder residues that are not visible?
Answer Greiss Test
Question Restoration 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.
Question When shoe and tire marks are impressed into soft earth at a crime scene, their preservation is best accomplished by ___________ and _______________.
Answer Photography and casting
Question A 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.
Answer points of comparison
Question The 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.
Answer False, 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.
Question A _________________is considered to be any impression, cut, gouge, or abrasion caused by a tool coming into contact with another object.
Answer tool mark
Question A careful examination of the impression can reveal important class characteristics, such as the _______________________________ of the tool.
Answer the size and shape
Question It is the presence of any minute imperfections on a tool that imparts _______________to that tool.
Question A 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.
Question Name a projectile that is not expected to show any evidential marks or impressions.
Answer A shotgun pellet
Question True or False? In collecting and packaging firearms evidence at a crime scene, an investigator must mark a fired bullet on its base for identification.
Question True 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.
Question True or False? In collecting and packaging firearms evidence at a crime scene, an investigator must mark an empty bullet on its base for identification.
QUESTION True 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.
Question Identify the two elements detected on the hands of an individual who has recently fired a bullet are: