Ballistics
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Explain why ballistic science is important?
Firearms were used in: 69% of the US murders 40% of robberies 21.6% of aggravated assaults
Handguns can be held and fired with ______. They are divided into ___ categories. Name them
one hand 3 revolvers semiautomatic pistols machine pistols
• Handguns Revolvers have a _____ to hold bullets and short _____. One pull of the trigger = ___ shot. Shell casting remains in the ______ after firing.
cylinder cartridges 1 cylinder
• Handguns Semiautomatic pistols have a ____ or a ____. Each shot = __ shot. empty shells are automatically _____.
magazine or clip 1 removed
• Handguns Machine pistols, automatic. It fires ______ (as long as ______). ___ similar to semiautomatic pistols.
repeatedly there is ammunition clip
Rifles often use a ____ or a sliding ___ to eject the spent cartridge. They can be ___ or _____.
lever blot automatic or semiautomatic
Shotguns don’t fire ____, but _____ filled with groups of ___. Those spread out in ____ pattern and the shot spread about an inch for each ___ feet of travel.
bullets shells pellets circular 3
Shotguns have no ___ in the barrel, so no ____ marks.
grroves identifying
Intact bullets are ____ found, so bullets often considered _______.
rarely trace evidence
How can we find the manufacturer of the gun?
chemical and physical composition of the bullet. powder in the bullets.
What information can be found with a recovered bullet?
1- a type of gun 2- trace evidence: paint, fibers 3- DNA flesh and blood.
What are the 3 limits of ballistic science when it comes to recovered bullets?
1- severely deformed 2- too small 3- damaged during recovery
____ bullets are soft, deform and fragment as they reach the target and they cause ____ damage.
Lead tissue
Lead ___ bullets are different than Lead bullets because they are mixed with ____ and ____. They deform and fragment (more/less) than lead bullets. Also, they have (more/less) penetrability.
alloy tin antimony less more
Semijacketed bullets have a thin layer of ____ on the side. They ____ and fragment upon impact.
brass expand
Fully jacketed bullets are ____ covered with brass. They have a ___ penetrating power. They can penetrate body armour which is why they are called ______. Their jacket is made of ___, ____ and other synthetics.
completely greater cop killer Teflon, nylon
How do we calculate the calibre of a gun? How do we calculate the gauge of a gun?
1- measurement of the internal diameter of the barrel. in inches or mm 2- number of balls that can fit in the barrel diameter - inverse relation.
The shell casing is the part of the bullet that ________. It retains marks such as: impression left by the ______ (centre-fire or rim-fire) _____ pattern _________ _____ or ejector marks.
remains after the powder explodes and the bullet is gone. firing pin breechblock headstamps extractor
The rifling pattern helps link a ____ to a _____.
bullet gun/gun type
Spiral grooves are inside the _____ and make the bullet ____. They make the shot more _____ and create marking that can be used in forensic.
barrel spin precise
depending on the manufaturer: the____ of the grooves, the _____ of the lands, the direction (______/_______), and the ____ of the twist.
depth width clockwise/counterclock degree
What are the three things that can link the bullet to a gun (simply with the rifling pattern)?
1- lands and grooves 2- twists 3- striations
What are the 3 limits of rifling patterns?
1- silencer 2- rifling patterns vary from barrel to barrel 3- when using a gun a lot, the grooves and the lands wear down.
What are the four steps to individualizing striations?
1- obtain intact bullet 2- compare the lab fired bullet + crime scene bullet 3- see if there is a match with a comparison microscope 4- identify or not the perpetrator