Chapter 17
The sequence of events in the firing of a bullet is
1. Pull the trigger 2. The tiny explosion 3. The main gunpowder supply ignites, and the pressure of the explosion pushes the bullet from the casing and into the barrel of the firearm. 4. The bullet follows the lands and grooves pattern of the barrel and begins its spiral before it leaves the barrel.
A cartridge consists of primer powder, gunpowder, a bullet (a pointed projectile), and the casing material that holds them all together.
A cartridge consists of primer powder, gunpowder, a bullet (a pointed projectile), and the casing material that holds them all together.
Compare and contrast an entry wound and an exit wound produced from a bullet
An entrance wound is much smaller compared to the exit wound. Also the GSR and any fabric that got attached would only be found on the entry wound and not the exit wound
Ballistics is the study of bullets and firearms, which are weapons capable of firing a projectile using a confined explosive, such as gunpowder.
Ballistics is the study of bullets and firearms, which are weapons capable of firing a projectile using a confined explosive, such as gunpowder.
Bullets fired from a firearm show patterns of lands and grooves that match the rifling pattern in the barrel of the firearm.
Bullets fired from a firearm show patterns of lands and grooves that match the rifling pattern in the barrel of the firearm.
Examination of the wounds on a body can determine where a bullet entered and exited the victim.
Examination of the wounds on a body can determine where a bullet entered and exited the victim.
T or F: Firing pin marks are found on the back of the bullet
False; back of the cartridge
T or F: Land and grooves help match a crime-scene bullet with its shell casing
False; land and grooves formed on rifling
Investigators look for the presence __________________ when trying to recreate a crime scene
GSR
Which are the following part of a cartridge?
Gunpowder, bullet, and prime powder
Gunshot residues found on victims, shooters, or nearby objects can help investigators recreate a crime scene. Investigators often use national databases to match crime-scene evidence to registered weapons.
Gunshot residues found on victims, shooters, or nearby objects can help investigators recreate a crime scene. Investigators often use national databases to match crime-scene evidence to registered weapons.
Handguns can be further classified as revolvers or semiautomatic firearms, depending on the feeding mechanism.
Handguns can be further classified as revolvers or semiautomatic firearms, depending on the feeding mechanism.
In addition to examining lands and grooves on a bullet, investigators can examine firing pin marks, breechblock marks, and extractor and ejector marks on a spent cartridge casing to match evidence at a crime scene with a specific firearm.
In addition to examining lands and grooves on a bullet, investigators can examine firing pin marks, breechblock marks, and extractor and ejector marks on a spent cartridge casing to match evidence at a crime scene with a specific firearm.
The Warren Commission concluded that
Lee Harvey Oswald worked alone in his assassination of President John F. Kennedy on November 22, 1963.
Modern firearms are divided into two basic types—long guns and hand-guns—that require two hands or one, respectively, for accurate firing.
Modern firearms are divided into two basic types—long guns and hand-guns—that require two hands or one, respectively, for accurate firing.
Who invented gunpowder?
More than one thousand years ago, the Chinese invented gunpowder.
What NIBIS stand for and how is it used to help solve crimes?
NIBIS is the *National Integrated Bullet Identification System* which has a computer files of ballistic markings of firearms used in previous crimes. It must be used in the prior cases that been recorded in the database to see if they can match the bullet found at a crime scene to a firearm that was used before.
You can use the _______________________to determine the length of the third side of the triangle, which is the height of the shooter above the horizon
Pythagorean Theorem
Why are bullets fired into a gel tank in a forensics ballistic lab?
So there will be no damaged done to the bullet as it being tested
The typical cartridge is composed of the following parts
The bullet the The primer powder mixture the anvil and flash hole the headstamp
The caliber of a cartridge is a measure of its diameter and is identified along with the name of the manufacturer on the headstamp.
The caliber of a cartridge is a measure of its diameter and is identified along with the name of the manufacturer on the headstamp.
Explain how the different parts of a gun and cartridge enable the bullet to be fired from a gun
The trigger releases the *hammer* that hits the *firing pin*, which causes the explosion of the *prime powder*. The explosion ignites the *gunpowder* in the casing. The *energy* of the expanding *gunpowder* forces the *bullet* through the *barrel*, which has *lands and grooves* on the inside. The *lands and grooves* causes the *bullet* to spiral as it travels as it passes through the *barrel*. This is where and how the *bullet* picks up these unique impressions caused from the inside of the *barrel*
Describe how investigators match a bullet to a firearm
They can match the bullet to a firearm by inspecting the lands and grooves- class on the bullet and matching the caliber of the bullet to the firearm. Also you can match up the striations- individualized
T or F: The amount of gunshot residue on a victim is usually proportional to the distance between the victim and the shooter
True
T or F: The lands and grooves of a barrel's rifling improve the accuracy of a bullet
True
Two major forces are acting on a bullet once it is fired: the forward force of the gunshot and the downward force of gravity.
Two major forces are acting on a bullet once it is fired: the forward force of the gunshot and the downward force of gravity.
Using at least two reference points, an investigator can recreate a bullet's trajectory and determine where a shooter was located during a crime.
Using at least two reference points, an investigator can recreate a bullet's trajectory and determine where a shooter was located during a crime.
What kind of information can be learned from gunshot residue (*GSR*) examination
You can see how far away the shooter was whether the shooter was close up or not to the victim
Cartridge
a measure of the inside diameter of a firearm barrel
Breechblock
a metal block that closes the aperture at the back part of a rifle or gun barrel
Firing pin marks
are impressions made on the bottom of the cartridge by the firing pin as it strikes the bottom of the cartridge when the firearm is shot
Reference points can be
bullet holes in an object, such as a wall or a window, or can be a bullet wound on a victim. Less-specific reference points include GSR on objects or piles of spent cartridge casings
Rifles fire
bullets
Bullets (and their cartridges) are named by
caliber and length.
while larger cartridges are usually
center fire
What are the difference between class and individualized fire arm evidence
class- lands and grooves individualized- striation
A firearm crime is often
complicated, and trajectory may be difficult to determine. Sometimes bullets ricochet, become damaged, and do not provide a direct path for measurement
The amount of GSR
decreases as the distance between firearm and victim increases.
The caliber of a bullet is related to its
diamater
Caliber also refers to the
diameter of the inside of a firearm's barrel
Albany Police Officer Joseph Gerace was trapped between parked cars in downtown Albany a few blocks from the State Capitol Building. Daniel Reed
drove his car erratically toward the officer and Gerace, fearing for his life, fired at Reed. One of the shots accidentally killed David Scaringe as he crossed a nearby street. Ballistics testing confirmed the shot that killed Scaringe was fired from Officer Gerace's firearm
For a firearm to work reliably, it must
effectively ignite the gunpowder.
Determining which wound is the
entrance wound and which is the exit wound is an important step in determining what happened at a crime scene.
The presence of GSR is usually found only around
entrance wounds.
A significant part of ballistics involves
examining used bullets and their spent cartridge casings for telltale markings left on them by the firearm that shot them.
Other marks left on spent cartridge casings include
extractor and ejector marks, which are minute scratches produced as the cartridge is placed in the firing chamber (by the extractor) and removed from the chamber after firing (by the ejector).
It is expected that several convicted criminals may win appeals if their conviction was based on
faulty evidence.
Trajectory can be calculated by
finding two reference points along the flight path of the projectile.
whereas shotguns
fire pellets or a single projectile called a slug.
A forensic science technician helps investigators in all stages of a criminal investigation. He or she will
gather evidence at a crime scene, analyze the evidence in a laboratory, and present reports to investigators as to the nature of the evidence. A forensic science technician may also be called to court to present findings as an expert witness during a trial. These technicians may specialize in a particular field of forensics, such as firearms or DNA analysis.
An archer will hit a target with
greater accuracy if there is a twist on the end of the arrow feathers.
all firearms explode
gunpowder
In revolvers, cartridges are
hand-fed into the revolving cylinder and have to be removed by hand as well.
Breechblock marks are produced as
he cartridge casing moves backward and strikes the breechblock. The markings are unique to the firearm and can be matched if the spent cartridge casings are found
Ammunition has a
headstamp—either a logo or name identifying the caliber and manufacturer. The headstamp is located on the bottom of the cartridge casing.
These cartridges are usually measured in
hundredths of an inch
Firing pin marks left on the spent cartridge casings can also be used to
identify a firearm
Shotgun shells are measured
in gauge
Primer
is a component of pistol. rifle, and shotgun rounds
Headstamp
is the markings on the bottom of a cartridge case designed for a firearm
Exit wounds are generally
larger, because as the bullet moves through the body, it may collect and carry body tissue and bone with it.
Investigators can also use _____________ trace straight-line paths that can help them determine the position of the shooter or shooters.
lasers
This rifling pattern
left on the bullet is specific to the firearm.
Small-caliber bullets, such as a .22 caliber, tend to
lodge within the body, while larger-caliber bullets will pass through.
Shotguns are examples of
long guns
Modern firearms are divided into two basic types
long guns and handguns.
Another way of determining entry and exit wounds is to
look at clues on the body near each wound. For example, if the bullet penetrates clothing first, fibers may be embedded in the wound pointing in the direction of penetration.
Semiautomatic pistols store cartridges in a
magazine (clip)
The chinese used gunpowder to
make fireworks and to shoot balls of flaming material at their enemies.
Firearms databases can be searched to
match crime-scene evidence to registered weapons.
What was the earliest firearm?
match lock
By examining the lands and grooves, a bullet investigators can
match to the gun from which it was fired
Bullets are normally made of
metal
the investigator might position the corpse as it was at the time of impact and use a
metal or wooden dowel to indicate the path of the bullet. Investigators can also use lasers to trace straight-line paths that can help them determine the position of the shooter or shooters.
he European method of naming firearm caliber uses the
metric system for measurement of cartridge diameter(mm)
Generally, centerfire cartridges are
more powerful than rimfire cartridges.
Gunshot residues containing
nitrates can stick to the person holding the firearm and leave evidence on the shooter.
Eyewitness accounts of a shooting are
not always accurate.
The semiautomatic permits the loading
of up to 10 cartridges into a magazine (clip), which is then locked into the grip of the firearm.
Technicians also collect non-organic materials, such as
paint flakes or glass fragments, to match with that of a suspect's car. They also collect fibers from clothing, rope, and other fabrics to compare with that, along with trace evidence such as hair, blood, etc.
he projectiles launched from these early firearms were very effective in
piercing suits of armor and wounding the enemy at a great distance.
Gunpowder is
potassium nitrate (saltpeter), charcoal, and sulfur. When ignited, it expands to six times its original size, causing a violent explosion.
handguns can be further classified as
revolvers or semiautomatic firearms
Smaller-caliber cartridges tend to be
rim fire,
a science technician applies
scientific knowledge and laboratory methods toward specific, real-world problems.
extractor and ejector marks are only produced from
semiautomatic and fully automatic weapons
To determine the distance between the shooter and hole in the car seat
set up a direct proportion using the two right triangles.
Revolvers hold
six cartridges in the cylinder.
entrance wounds are
smaller than exit wounds, because the skin is somewhat elastic, and it stretches when a bullet enters the body.
These residues are the traces of
smoke and particles of unburned powder carried sideways from the firearm by the expansion of gases as the bullet is fired.
lands and grooves cause a bullet to
spiral when exiting the barrel of the gun, much in the same way a football spirals when thrown.
Long guns,
such as rifles and shotguns (Figure 17-4), require the use of two hands for accurate firing.
To get a known bullet for comparison, investigators...
test-fire the weapon into a water tank or gel block. This captures the bullet without damaging it. Then, they can compare the markings on known bullets with those on the suspect bullets.
The distance between the weapon and the victim can be determined by
the GSR pattern on the body of a victim.
two important databases are
the National Integrated Bullet Identification System (NIBIS), Drugfire, which were merged to form National Integrated Ballistics Network (NIBIN).
He accused the prosecution of trying the men as part of
the Red Scare of 1919-1920
Because the bullet moves through the barrel, the caliber of ammunition should match
the firearm that shoots it. If a bullet is removed from a wound or crime scene, its caliber can link it to the weapon used to fire it.
Which of the bullet best describes the trajectory?
the path of the flight of a bullet
Bullet
the projectile that is released when a firearm is discharged
Lands and Grooves
the ridges (lands) and depressions (grooves) found on the inside of a firearm's barrel that are created when the firearm is manufactured
To determine the position of a shooter, the distance between
the shooter in the building and the bullet hole in the car seat must be determined. This requires at least two reference points from which to project a line back to the source of the shooter in the building
The larger the gauge number
the smaller the inside diameter of the barrel would be.
Firearms examiner
they collect, identify, classify, and analyze physical evidence related to criminal investigations.
Investigators may also have to use ________________ to determine a shooter's whereabouts during a crime.
trace evidence, such as footprints, fingerprints, or DNA samples from hair or saliva,
This position as a forensic science technician requires a
two- to four-year education that includes courses in chemistry, physics, math, and criminal justice.
each gun has a
unique pattern. It is impossible to produce two identically rifled gun barrels. As a gun is fired, the barrel marks each bullet with its own unique pattern. Therefore, a bullet can be matched to the specific gun from which it was fired.
GSR can be removed by
washing, but chemical testing can often detect residue despite the attempted removal.
An important part of a ballistics investigation is determining
where a shooter was located during a crime. Investigators look for clues at a crime scene to help them calculate a bullet's trajectory to figure out where a shooter discharged the firearm.
