Chapter 9 - Firearms, Tools, and other impressions

What is the procedure for casting an impression?

(1) Remove any debris not relevant to the impression (2) Spray the impression with aerosol to harden (3) Knead dental stone and water mixture until you've reached the desired consistency (4) Pour this mixture over the impression (5) Fill the impression with the mixture and allow 24-48hrs to dry before removal

List the Classifications of Handguns

(1) Single-Action (2) Double- Action

What characteristics are present when a victim was shot up to 18in away?

A halo of vaporous lead will surround the bullet's entry hole

This concept entails the capture and storage of appropriate markings on bullets and cartridges test-fired from handguns and rifles before being sold to the public

Ballistic Fingerprinting

What elements are always found in primer residue?

Barium and Antimony

What elements are always found in gunpowder residue?

Barium, Antimony, and Lead

Why has the dermal nitrate test become a unfavorable method of detecting the presence of nitrates?

Because of its lack of specificity

What software system contains a cartridge-case analyzing module

Brass Catcher

What is the rear part of a firearm barrel

Breech Face Mark

mixture of carbon, dirt, lubricant, primer residue, and lead wiped off the bullets surface as it passes through the target

Bullet Wipe

What software system contains a bullet analyzing module

Bulletproof

What is the key material used for developing a cast?

Class 1 Dental Stone

When a heavy concentration of residue surrounds the bullet's entrance hole Loose fibers show scorch marks Synthetic fibers may show signs of being melted & The blowback of muzzle gases produce a stellate tear-pattern around the hole What distance was the victim shot from?

Close contact or within an inch

Maintained by the FBI This system emphasized the examination of unique markings on the cartridge casings expended by the weapon Emphasized the use of cartridge-case imagery

DRUGFIRE

What is tattooing/stippling?

Debris that results from gunshot residue hitting the target

What are the major issues in tool mark comparison?

Difficulty in duplicating the tool mark left at the crime scene

the assessment of the distance from which a handgun or rifle was fired

Distance Determination

the hammer is automatically cocked when the trigger is pulled

Double-Action Handguns

In what instances are Marlin rifles distinct?

During rifling, these rifles are rifled through the use of micro-grooving. They can have anywhere between 8-24 grooves impressed into their barrels

A discipline primarily concerned with determining whether a bullet or cartridge was fired by a particular weapon

Firearm Examination

How do firearms work?

Firearms are based off a simple explosion The pulling of a trigger releases the weapon's firing pin causing it strike the primer. This in turn ignites the powder The gases generated by the burning gunpowder propel the bullet forward through the barrel simultaneously pushing the cartridge case back with equal force against the breech face mark

What is the significance of the comparison microscope in firearms examinations?

Firearms examination began with the introduction of the comparison microscope It allows two bullets to be compared simultaneously

If there is no powder residue on the victim but there is a dark ring around the perimeter of the entrance hole, then the victim was shot

From three or more feet away

Between Gun Powder Residue and Primer Residue which is mostly found on the target/victim after a shooting?

Gun Powder Residue

These firearms are designed to be held and fired with one hand

Hand Guns

What are the different areas of ballistics?

Internal External Terminal

What are the functions of NIBIN?

It produces database files from bullets and cartridge casings retrieved from crime scenes or test fires from retrieved firearms

With the exception of .22's, all primers contain a blend of

Lead Barium Antimony

What type of guns yield a longer range and accurate shot?

Long Guns

What did Newsome say was the best weapon for mass shootings?

M-16

IBIS

Maintained by ATF, this system processes digital microscopic images of identifying features found on both expended bullets and cartridge cases

What is the General Rifling Characteristic File?

Maintained by the FBI, it contains class characteristics for known weapons

How were the Beltway Snipers apprehended?

Malvo bragged to a priest about his involvement with a murder in Montgomery. The fingerprint left behind at the robbery belonged to Malvo. Malvo's fingerprints were on file with the Immigration and Naturalization Service

Between Gun Powder Residue and Primer Residue which is mostly found on the shooter after a shooting?

Mostly Primer Residue, but traces of Gun Powder Residue can be found

What is the principle tool used in electrostatic lifting?

Mylar film

Were the beltway snipers really snipers? Why or Why not?

No because they did not use a sniper weapon

What process forms the spiral grooves in the bore of a firearm

Rifling

The Broach Cutter

Rifling Method that entails that as the broach passes through the barrel, it simultaneously cuts all grooves into the barrel at the required depth

The Mandrel-Rifling Hammer-Forging Process

Rifling method where the mandrel is inserted into a slightly oversized bore, and the barrel is compressed with hammering into the mandrel's form

The most important consideration in handling a firearm is

SAFETY!

When linked to an x-ray analyzer, an analysis of the particles can be conducted

SEM Testing

What case did Goddard provide testimony in?

Sacco and Vanzetti

microscopic primer and gunpowder particles on an adhesive are found with a

Scanning Electron Microscope- the SEM

the magazine is contained within the grip, and these guns fire one shot per trigger pull

Semi-Automatics

What did Newsome say was his preferred weapon for raids?

Shotguns

require the hammer to be manually cocked each time before the trigger is pulled

Single-Action Handguns

List the three most common types of handguns

Single-Shot Revolvers Semi-Automatics

can only fire one round at a time

Single-Shot Hand Guns

List the class characteristics of a tool mark or impression

Size, shape, and design of the tool mark/impression

What substance is used to cast impressions in snow?

Snow Impression Wax

List the individual characteristics of projectile

Striation markings

List the Physical Evidence recovered in cases involving a firearm

Striations Gun Shot Residue Primer Residue Shell Casings Fingerprints on Cartridge Casings DNA

In general, this method produces a low-rate of positive results because of the short period of time that residue remains on the hands

Swabbing

What technique requires residue to be removed by swabbing both the firing and non firing hands with cotton that has been moistened with five percent nitric acid?

Swabbing

________ or ________ cannot be used to detect firings of most .22 caliber rimfire ammunition

Swabbing or the use of an adhesive

Damage when the target is striked

Terminal ballistics

What method requires a steel plug impressed with the desired number of grooves, under extremely high pressures, being forced through the barrel?

The Button Process

measures the diameter of the bore and the diameter of the bullet recorded in the hundreths of an inch or in millimeters

The Caliber

What techniques can be used to detect primer residue on hands?

The Dermal Nitrate Test Swabbing SEM Testing

What are the distinct characteristics of a rifle that make them different than shotguns?

The barrel has spiral grooves and lands Striation markings can be found on projectile when fired

List the characteristics of a shot gun

The barrel is smooth and can be narrowed in order to concentrated shot when fired Shells passing through the bore are not impressed with striation markings Can be single or double-barreled

What variables affect the shot pattern in cases where a shotgun was used?

The barrel length The size and quantity of the pellets being fired The quantity of powder charge used to propel the pellets The choke of the gun under examination

What was the significance of the bullets used in the murders carried out by Sacco and Vanzetti

The bullets were no longer being produced so ballistics examiners were not able to use this ammunition or similar ammunition for test fires to determine if that was the weapon used in the crimes

What is the most important tool used in firearms examination?

The comparison microscope

What is the gauge?

The diameter of the barrel It is determined by the number of pellets with the same diameter as the barrel that would equate a pound

In determining distance, if the weapon is not present, how would the examiner make this determination?

The examiner would then have to analyze characteristics around the bullet hole

What should you do if a firearm is recovered from an underwater location?

The firearm should be transported in a receptacle containing enough of the same water it was found in to keep it submerged. This prevents rust from developing

What aids in the formation of striation markings on bullets?

The firing pin The ejector The extractor The Breech Face Mark

What holds the ammunition in a firearm?

The magazine

An identification tag for a firearm includes:

The serial number Make and model The investigators initials

CONS of the SEM

The time it takes to conduct the analysis

If the target was shot up to twenty-five inches away then..

There will be scattered specks of unburned and partially burned powder grains No soot will be present Scattered gunpowder particles are deposited at a firing distance of up to thirty-six inches

What is a major strength of semi-automatic weapons?

They have higher bullet capacities and less reloads

What portions of the hand will residues mostly deposit on?

Thumb Web Back of the firing hand

any impression, cut, gouge, or abrasion caused by a tool coming into contact with another object

Tool Marks

When using a comparison microscope, what illumination is used to examine hairs or fibers?

Transmitted

What is the most popular method of removing gunshot/primer residues from a surface?

Using an adhesive or adhesive tape to lift the residue particles

When using a comparison microscope, what illumination is used to examine bullets and cartridges?

Vertical or Reflected

What are the methods for testing firearm evidence?

Water Tank Recovery System Cotton Recovery Tank

In what instance would an investigator need to cast an impression?

When the impression is in soft earth

List the different methods to collecting tool mark evidence

With reason, the entire object with the tool mark can be submitted to the lab When the tool mark cannot be removed, a photo must be taken and a cast must be made

How are serial numbers recovered in firearms?

With the application of a etching reagent

How long should cast dry for?

air-dried for 24-48hrs

Why are serial numbers able to be restored?

because they are imprinted under a permanent strain that lies beneath the original numbers

A bullet travels through the _____ before leaving the barrel

bore

Trace evidence recovered from tools/tool marks

chips of paint adhering to the tool mark or tool

How is distance usually determined?

comparing the powder residue pattern on the victim's clothing or skin to test patterns made by firing the suspected weapon at varying distances from a target

External Ballistics

everything that occurs outside the weapon that effects the shot (wind, rain, gravity)

Long Guns

firearms designed to be fired while resting on the shoulder Also known as rifles and shotguns

What term is used to describe the level of harm of the bullet?

gravity of harm

Revolvers

have several firing chambers and when fired, the cylinder automatically rotates clockwise or counter-clockwise

PROS of the SEM

high magnification, high resolution, and great depth of focus

everything that happens inside the weapon (the explosion, the lands and grooves)

internal ballistics

What is the major advantage of the SEM?

its enhanced specificty

_______ are high and cause the deepest cuts in striations

lands

When would electrostatic lifting be utilized?

lifting and preserving dust impressions

What type of gun terms the ammunition as shell

shot guns

The SEM characterizes primer particles by

size, shape, and chemical composition

Entry wound is ______, exit wound is _______

small, large

What was used to determine that Sacco and Vanzetti were guilty of the crimes?

the Comparison Microscope

What test for gunpowder residue requires the application of hot paraffin or wax to a suspect's hand and what color yields a positive reaction?

the Dermal Nitrate Test & Blue

What two-part chemical reactive test is used to examine patterns of gunpowder residues around bullet holes and test for the presence of nitrites

the Greiss Test

How is distance determined in cases where a shotgun was used?

the distance determination can be estimated by measuring the spread of the discharged shot, As distance increases, the pellets progressively separate and spread out

What is the bore?

the interior of a firearm barrel projectile pass through the bore before leaving the firearm

What is the choke?

the narrowing of the barrel

List the class characteristics of projectile

the number of lands and grooves the direction of their twist

What is used to determine if a person has recently handled or fired a weapon

the presence and amount of barium and antimony on the relevant portions of the suspects hands

What is the comparison microscope used for in firearms examination?

to compare striation markings on bullets

List the individual characteristics of a tool mark

wear, random nicks and breaks, and other damages that the tool/impression acquired through wear and use