Unit 10
___ is the diameter of the bore of a rifle before the rifling grooves are cut. It is also a measurement used to describe the diameter of the cartridge in inches.
caliber
The products of most combustion reactions are ___ ___ and ___, but the initial burning of wood can release volatile compounds like formaldehyde.
carbon dioxide; water
A ___ is a case, usually made of brass or copper, containing the powder charge, the primer, and the bullet.
cartridge
The function of the ___ to contain the pressure and prevent outward expansion of gases after the priming compound is ignited. Often the end of the cartridge cylinder touching the bullet is slightly crimped to hold the bullet until it is fired.
cartridge
___ lines means the glass shattered because of impact and ___ edges mean the heat caused the glass to break.
curved; smooth
Because of a slower reaction speed, a low explosive does not have a technical detonation, but a ___.
deflagration
What is the extremely rapid burning of a material?
deflagration
What is the first priority of an explosives unit?
find the explosive device. and render it as safe as possible
Who was the Molotov cocktail created by to mock the Soviet foreign minister?
finnish military
What is the chemical reaction in which bonds are broken and molecules are rearranged to produce new substances?
fire
Once the evidence is in the lab, the technician will ___ the can to release any accelerants that may be present. Once any accelerants are released, the technician will obtain a sample of the vapors released for testing by gas chromatography (GC) and mass spectrometry (MS). This method of testing is accurate and sensitive and can detect amounts of accelerant as small as 1/1000 of a drop on a piece of evidence.
heat
A ___ caliber cartridge is 22/100ths of an inch at the widest point.
.22
When was gunpowder believed to be invented?
13th century china, turkey, or europe
When and what was the first gun that operated that operated with a firing mechanism?
14th century; matchlock gun
The sawed-off shotgun is a shotgun in which the barrel has literally been sawn off to ___ inches or less.
18
What is the auto-ignition temperature of wood?
572 degrees f
What are the procedures for taking a gun into evidence?
First record the position of the hammer, safety, and all fired and unfired ammunition.
What is the computerized image analysis system that records striated images from bullets and cartridge cases for comparison in a national database?
IBIS
How does a gun fire?
Initially a cartridge enters the chamber and the firing pin is held back with a spring. When the trigger is pulled, the spring releases sending the firing pin forward. The firing pin then hits the primer cap of the cartridge, igniting the primer powder which sparks through the flash hole to the gunpowder. The gunpowder is the main propellant supply. The pressure of the exploding propellant pushes the bullet from the casing into the barrel. The bullet follows the lands and grooves produced by rifling and spirals out of the barrel. For every action there is an equal and opposite reaction. The explosive force of the bullet out of the barrel is met with a sharp recoil of the gun slide which ejects the casing, and a new cartridge is forced into the chamber.
An example of an incendiary device is a ___ ___, which is a glass bottle containing a flammable liquid and a cloth wick protruding from the mouth of the bottle.
Molotov cocktail
What three things does something need to be considered a firearm?
a charge material, a projectile, and a barrel to fire from
The discolored circle immediately surrounding the entrance wound is called an ___ ___, produced by the bullet's friction as it pierces the skin.
abrasion ring
Rifling is used to increase both ___ and ___ on a firearm.
accuracy; range
Invasive methods that also eat away the metal are ___ ___ which eats away the damaged metal and leaves the deeper metal intact, or high frequency vibration which also eats away the metal that has been disturbed and reveals the underlying serial print.
acid washing
If steel beams have buckled in a building that is on fire, it suggests that...
an accelerant was used
You arrive at the scene of an extinguished building fire and notice that there are multiple points of origin. What do you suspect?
an accelerant was used
What is it called when a fire is set intentionally on a property?
arson
How many times does Jason Roach, Firearms examiner at the Richland County Sheriff's Department test fire to obtain bullets with striae for comparison to evidence?
at lease three
Where should a suspected arson case begin?
at the areas that are the least burned
What is it called when when the object reaches a temperature, it will combust or burn in air without a spark or ignition source?
auto-ignition temperature
A different set of guns known as fully ___ ___, are not common and are illegal without a special permit. It weapon continuously fires rounds while the trigger is pressed and held.
automatic weapons
What is the blowback of blood droplets onto the shooter due to the energy of the impact as the bullet enters the victim.
back spatter
___ is the study of what happens to moving projectiles in the barrel (internal ballistics) and in flight (external ballistics) including their trajectory, force, impact, and penetration.
ballistics
GSR contains...
barium nitrate
The ___ is the iron or steel tube of a firearm through which the bullet or round passes when the weapon is fired.
barrel
What are the four major parts of a gun?
barrel, muzzle, breech, trigger, and hammer
What are common combinations of ingredients used by terrorist groups to make bombs, and are kept in databases maintained by the FBI, ATF, and the National Fire Incident Reporting System that can be used to analyze evidence from explosive sites?
bomb signatures
The ___ is the interior tunnel down the barrel of a firearm through which the projectiles travel.
bore
The ___ is the portion of the gun that contains the firing mechanism which is generally located at the back end of the barrel. Bullet cartridges are loaded into the breech end of the gun for firing.
breech
The ___ is a projectile made of varying materials: lead, steel, copper, and sometimes rubber. Often, lead bullets are plated or jacketed with copper, nickel, or Teflon to keep the bullet's shape during expulsion from the barrel and flight to the target.
bullet
Bullets also leave lead residue called "___ ___" on the clothing of the victim, and if the shooter was within three feet of the victim, there will likely be gunshot residue on the surface of the victim's clothing which can be tested for the presence of lead, barium, and antimony salts.
bullet wipe
When a bullet enters a body, it enters with such force that it causes temporary shock waves to be distributed throughout the tissues. These pressure waves stretch the tissue to create temporary spaces or cavities in the body which quickly return to normal size, but often not without damage. This phenomenon is called ___.
cavitation
A shot at ___ range can leave residues of these materials around the wound and can also burn skin.
close
What was the first mass produced multi-shot weapon and what year?
colt revolver invented by samuel colt in 1830s
What chemical reaction associated with fire is a type of oxidation-reduction (redox) reaction?
combustion
What is the rapid recombination of oxygen with other substances and is accompanied by light and heat?
combustion
What is the theory where if you have so many sets of striation on the bullet itself or groups of them on the cartridge case then you can say it is a good indicator to say yes These came from the firearm or no these did not come from the firearm as I said or inconclusive?
consecutive matching strike
A ___ shot, when the weapon is held against the surface of the target, will not leave residues around the wound, but rather in the underlying tissues through which the bullet has passed.
contact
Under extreme heat, such as when accelerants are used, investigators look for ___ patterns on the walls, ceilings and floors. A pattern that resembles ___ ___ may also be found in these cases.
crackle; alligator skin
Cavitation can cause severe damage to ___, less flexible tissues such as the kidney, liver, muscle, and brain.
denser
The rate or speeds of ___ of reactions are what classify explosives as either high explosives or low explosives.
detonation
___ is the sudden and violent release of mechanical, chemical, or nuclear energy from a confined space which creates a shock wave that travels at supersonic speeds.
detonation
In more ___ tissues, the tissue snaps back and repairs much more quickly. Cavitation can cause minor damage to more serious damage.
elastic
An ___ wound can be identified by an abrasion ring, soot, stippling, muzzle imprints, or carbon monoxide burns.
entrance
Beveling indicates an ___ wound.
exit
Often ___ wounds are larger and bleed more profusely because the bullet has been slowed and flattened somewhat by passage through the body thus the bullet must exert force across a wider area to escape, but it is better to search for confirmation clues.
exit
T or F: Flash point is much higher than the auto ignition temperature in most fuels.
false
T or F: If something is just smoking, it is not considered spontaneous combustion.
false
T or F: Revolver barrels aren't rifled.
false
T or F: Striations are considered class evidence.
false
T or F: There can't be two points of origin of a fire.
false
The three requirements for fire are often referred to as the...
fire triangle
The ___ ___ is the part of the breech mechanism that strikes the primer of the cartridge. When it strikes the primer of the cartridge, it makes a unique marking on the back of the cartridge that can be examined to verify matching bullet cartridges.
firing pin
What is the temperature at which a liquid fuel produces enough vapor to ignite when exposed to a flame or spark?
flash point
How are flash points tested?
flash point tester
What is the measurement of shotgun bores derived from the number of bore-sized balls of lead to the pound?
gauge
The primary constituent of wood is cellulose which is a ___ ___.
glucose polymer
In the ___ ___, photo paper is placed over a bullet hole and heated with an iron containing a weak vinegar solution. The vinegar solution is applied to the area of the bullet hole using the steam feature on the iron. The vinegar reacts with the photo paper to make the nitrites visible as an orange color pattern on the photo paper. Because this method does not destroy the item of evidence, it is usually conducted first followed by other subsequent testing of clothing.
griess test
The ___ ___ is a chemical test that is used to develop patterns of gunshot residues around bullet holes on clothing or other fabric.
griess test
___ are spiral cuts into the bore of a barrel that give the bullet its spin or rotation as it moves down the barrel.
grooves
The cutaway portions of the rifling are called ___ and the uncut portions are called ___.
grooves; lands
Why is lead styphnate used in the primer space rather than plain gunpowder?
gunpowder has to be ignited be a flash or flame whereas lead styphnate can be ignited by frictional impact
What consists of burned and unburned gunpowder, vaporized, and particulate lead, primer residues of lead, barium, and antimony?
gunshot residue
___ ___ consists of burned and unburned gunpowder, vaporized lead, powdered lead, and primer residues of lead peroxide, barium nitrate, and antimony sulfide.
gunshot residue
The ___ is the part of a gun that hits the primer or firing pin, or explodes the primer cap, and causes the gun to fire.
hammer
___ ___ are substances that react and expand faster than the speed of sound in the substance which produces an extremely loud detonation. They include dynamite (nitroglycerine), C4, and TNT (trinitrotoluene), and are used in commercial and military blasting.
high explosives
Any explosive device such as a homemade bomb made non-commercially with the explicit intention of exploding it is called an...
improvised explosive device
IED
improvised explosive device
How is evidence from a fire packaged and transported?
in airtight containers, often new paint cans
Where is an arsonist most likely found?
in the crowd watching the fire
What are devices specifically created to start fires called?
incendiary devices
___ ___ wounds are also accompanied by eye hemorrhage due to the severe fracturing of the skull as the bullet exits.
intraoral gunshot
An ___ ___ ___ is used to chemically detect explosive residues on objects from the explosion site.
ion mobility spectrometer
IMS
ion mobility spectrometer
Who and what year was the first semi-automatic repeating pistol invented?
josef laumann; 1892
___ are the raised areas between two grooves in the rifling of a gun barrel that impart grooves on the bullet.
lands
The areas with the ___ scales of alligator skin patterning indicate that the fire was hottest in that area.
smallest
A shotgun, by definition, is simply a ___ firearm.
smoothbore
When a bullet exits a body, the hole left by the exiting projectile is normally ___ than the entrance wound. However, this is not always the case. The size of the wounds is dependent upon the velocity, shape, and size of the bullet as it impacts the tissue, and the type of tissue through which the bullet is traveling.
larger
If gunpowder is deposited closely around the edges of the entrance wound, it is called ___ contact. In these wounds, we generally see soot on the skin which can be washed off to reveal stippling wounds under the skin.
loose
What does the sodium rhodizonate test indicate?
loosely determines muzzle-to-target distance in close range shootings based on the distance at which vaporized lead is detected or not detected
Black powder, fireworks, and smokeless powder are classified as...
low explosives
Liquids with ___ flash points burn easier and are much more prone to causing fire hazards.
lower
Both automatic and semi-automatic weapons use a ___ which is the part of a repeating firearm that holds the cartridges or shells in position ready to be loaded one at a time into the chamber.
magazine
An example of a noninvasive way of restoring a serial number is ___. A magnetic particle solution is sprayed on the area of interest and the firearm is exposed to an electromagnetic field. The magnetic field causes the magnetic particles in the solution to align and reveal the original number.
magnaflux
Gun barrels are made by hollowing out a solid bar of steel with a drill. This process results in ___ drill marks that are random and irregular.
microscopic
Gunshot blood spatter, however, results in a fine ___ pattern which is a spray of micro-droplets less than 1 mm in diameter due to the high velocity of impact and travel.
mist
The ___ is the forward end of a barrel. Historically, many of the earliest firearms were loaded with it which meant that the ammunition was loaded from the front end of the barrel with a propellant such as gunpowder. While this method worked most of the time, the ___ loader was time-consuming to load and did not allow for more than one shot per loading. It also was prone to misfires and led to more dangerous conditions.
muzzle
Typically, a nine millimeter handgun will fire what type of cartridge?
only 9 mm
What are the three required elements needed to produce a fire?
oxygen, heat, and fuel
In most arson cases, a ___ product is used for the accelerant and a match is used as the ignition device.
petroleum
A ___ is a semi-automatic firearm designed to be held and fired with one hand.
pistol
The focus of an arson investigation should hinge on finding the ___ ___ ___ to see if an accelerant or ignition device can be located.
point of origin
The ___ is a device that contains lead styphnate, an explosive material that is impact sensitive.
primer
___ ___ can be bullet holes in objects or victims such as an entry point and exit point on a victim. A bullet does not travel in a straight line over a long range, but rather in an arc. This is due to the force of gravity on the bullet. The force of gravity on a fired bullet and the force of gravity on a bullet dropped to the ground are exactly the same. Hence, a bullet fired from exactly 5 feet high and a bullet dropped from a height of five feet will hit the ground at the about the same time, given that the ground is level, and drag and gyroscopic effects of rifling are ignored.
reference points
A ___ is a handgun having a revolving cylinder with several cartridge chambers that may be fired in succession. It is not considered a semi-automatic weapon because each shot that is chambered requires a trigger pull.
revolver
What type of gun has cartridges stored in a cylinder?
revolver
When the fire pattern is ___-shaped from the point of origin, this is considered a red flag and arson is usually suspected. This pattern is typically produced when fire follows the path of an accelerant that has been poured or sprayed in the area.
ribbon
A ___ is a shoulder firearm with a rifled barrel designed to fire one projectile, or bullet, at a time.
rifle
Gun barrels can be ___ or ___.
rifled; smooth
What are the four most common types of guns?
rifles, pistols, revolvers, and shotguns
Why don't shotguns have rifled barrels like pistols and rifles do?
rifling helps a bullet spiral so that it travels in a straight line improving accuracy but shotguns don't need rifling because they fire shot pellets which are designed to have a wider spread
Rifles and handguns have ___ whereas shotguns have ___ barrels.
rifling; smooth
The ___ helps hold the cartridge in position in the firearm in a centerfire cartridge.
rim
In a ___ ___, the primer compound is contained in the rim.
rimfire cartridge
What are two things often used by bomb squads to render something safe?
robotic devices and x-rays
Who was the first to obtain a patent for the revolving mechanism as well as the first to make firearms more widely available to the public?
samuel colt
The following reasons: to make the weapon easier to conceal, to make it easier to shoot one-handed, and to force the shot to spread in a wider pattern when it exits the gun, are reason to...
saw off a shotgun
A ___ weapon fires one round with each individual trigger pull without the need to reload or reset the gun after each shot.
semi-automatic
Every weapon contains a ___ ___ etched into the working metal components.
serial number
What is a cartridge as known as?
shell casing
A ___ is a firearm with a smooth bore, or smooth barrel without rifling, designed to fire shells containing small pellets called shot. Shot pellets spread out and hit a wider target area than a bullet which is designed to be more pinpoint accurate.
shotgun
What two types of gun is not rifled?
shotgun and fully automatic weapon
After an empty magazine is exchanged for a full one, depressing the ___ ___ will release the slide from a locked position and chamber the first round of the fresh magazine.
slide release
Upon firing a pistol, the ___ recoils from the energy of the blast, ejecting the spent cartridge through the ___ ___.
slide; ejection port
___ are heavily grooved on the outside to provide grip so the operator can pull the part backwards to check for chambered rounds through the ejection port.
slides
A ___ ___ test may be conducted to detect any lead residues in the areas of suspected gunshot residue. It is conducted by spraying the area of suspected gunshot residue with a solution of sodium rhodizonate. If lead residues are present, the sprayed area will turn a bright pink color on the item. To confirm the presence of lead, the bright pink areas are then covered with dilute ___ ___. If the area turns blue in the presence of hydrochloric acid, the presence of lead is confirmed.
sodium rhodizonate; hydrochloric acid
How do you calculate the distance of a shooter?
sohcahtoah
What are the two ways in which gunpowder exits the muzzle of a gun?
soot or fouling which can be washed off the skin and burned or unburned particles in the skin
Rifling is the ___ grooves that are cut into the inside barrel surface to cause a bullet to spin, thereby stabilizing it.
spiral
___ ___ is a fire caused by the natural heat that is produced by internal reactions of a substance in the presence of oxygen.
spontaneous combustion
___ ___ often involves a combination of factors including low auto-ignition temperature, insufficient ventilation causing excess heat to build-up, bacterial fermentation, and the presence of oxygen.
spontaneous combustion
The following are explantations of... The victim was disabled or incapacitated due to illness, obesity, or intoxication and was too close to a heat source such as a lit cigarette, candle, or heater unit. Due to the incapacitation, the victim was unable to put out the fire as it burned. "The wick effect" hypothesis says that a heat source, such as a lit cigarette, burns a victim causing the skin to split. The split skin allows subcutaneous fat beneath the skin to heat and melt. The melted fat then soaks into the clothing or furniture that that victim is seated or lying upon. The fabric acts like a wick in a candle to keep the body burning until the fat is combusted and no longer soaking the furniture. Normally the core body is consumed by the flame leaving only the lower arms and legs. This hypothesis seems to be the most consistent explanation and is backed up by evidence from both animal trials and from actual cases of burned victims. It also explains why the fire is relatively confined and does not spread to other areas such as the carpeting or other objects in the room.
spontaneous human combustion
What is another name for the scratches left on the surface of the bullet after firing the gun?
striations
If the explosion is suspected to be terrorist-related, the FBI has a special lab that they use in order to examine the evidence called ___ ___ ___ ___ ___, and it is located at FBI headquarters in Quantico, Virginia.
terrorist explosive device analytical center
TEDAC
terrorist explosive device analytical center
What is the cause of heat in fire?
the broken and newly formed chemical bonds
Why do caliber measurements of barrel bores and cartridges have to be the same?
the caliber of a cartridge is the diameter at the widest part of the width of the cartridge, and it would make sense that it matches the bore diameter as the cartridge must fit snugly within the barrel.
How does a firearms expert determine what bullet and gun were used?
they will first evaluate the caliber of any bullets or casings found at the crime scene as well as the suspected weapon if it is in custody. next, the casings will be inspected using a comparison microscope for any unique markings caused by the specific firing mechanisms within the gun and the way in which the gun was manufactured
If one handgun and only one bullet are found at a crime scene involving a homicide, how will firearms investigators test the striation patterns on that bullet?
they will test fire a bullet through the gun and match the striations on that bullet with the striations on the evidence bullet
The most reliable place to find gunshot residue (GSR) is on the webbing of skin between the ___ and ___ finger.
thumb; index
If all gunpowder residue is on the edges or deep within a gunshot wound, or the skin immediately surrounding the entrance is burned it indicates ___ contact of the gun muzzle to the skin of the victim.
tight
Which type of gunshot wound will likely not produce stippling?
tight contact
Other factors that can influence the ___ of a bullet are wind, atmospheric pressure, temperature, and humidity. Investigators can use lasers to trace a straight-line path between the reference points to help determine the position of the shooter based on the idea that the shooter would have discharged the firearm somewhere along that line.
trajectory
The ___, or the path a bullet travels from muzzle to impact, of a projectile can be determined if two reference points for the projectile can be found.
trajectory
The hammer is activated by pressing the ___. It is defined as the lever that activates the firing mechanism of a gun.
trigger
T or F: Combustible liquids are almost never entirely consumed during a fire.
true
T or F: Criminals will file or scratch the serial numbers off to prevent authorities from tracing the purchase record of the weapon.
true
T or F: Grit, rust, and mutilation upon impact make it rare to find a perfect match all the way around a bullet.
true
T or F: Handgun barrels are rifled.
true
T or F: Impressions left by firing pins are considered class evidence.
true
T or F: Intense heat causes fingerprints to stick to many surfaces.
true
T or F: No two rifled barrels, even those manufactured in succession, will have identical rifling impressions.
true
T or F: Redox reactions are most often exothermic.
true
T or F: Spontaneous human combustion (SHC) is considered a myth.
true
T or F: Substances that combust spontaneously have low auto-ignition temperatures such as compost piles, wood piles, peat, straw, hay, coal, pistachio nuts, large manure piles, and in some cases cotton and linen.
true
T or F: The origin of the fire is found at the bottom point of the V-shaped cone.
true
The best way to pick up a weapon is with ___ fingers on the trigger guard or the checkered portion of the grip which rarely yields prints. Never pick up a suspect's firearm by sticking a pencil in the barrel.
two
Under normal circumstances, fire tends to move up and out forming a ___-shaped pattern from the point of origin.
v
What is the condition that facilitates a flash point?
vaporization of a liquid due to weak molecular bonds
Victims A and B survive gunshot wounds to the abdomen. Victim A displays a half-inch area of reddened skin around the entrance wound. Victim B displays a one-inch area of reddened skin around the entrance wound. Which victim was likely shot from a closer distance?
victim a
A ___ ___ is produced when a person or an object blocks the path of blood which produces a void, or absence of blood staining in an otherwise continuous bloodstain pattern.
void pattern
Fuels such as gasoline vaporize or evaporate easily because the intermolecular forces that hold molecules together in the liquid are ___.
weak
Once all testing is completed to locate and confirm gunshot residue, the investigators will then test the weapon with the same type of bullets at various distances to come up with a minimum and maximum distance required to reproduce the same general gunshot residue pattern. Shots are fired at various distances into targets holding ___ ___ and ___ ___. These cloth targets are inspected for gunshot residue patterns consistent with the evidence collected and can then be used as an approximation for the distance in which the gun was fired from the victim or object.
white cotton; denim fabric
What is the oxidation reaction for glucose?
𝐶6𝐻12𝑂6 +6𝑂2→6𝐶𝑂2+6𝐻2𝑂+ℎ𝑒𝑎𝑡
