Oral Board

What are the three areas of ballistics?

1) Internal-the study of the projectile as it moves along its path to the target. 2) External-the study of the flight of the bullet as it moves along its path to the target. 3) Terminal-the study of the impact the projectile makes when it hits its intended target.

What are the difference types of light sources with a comparison microscope? Describe each.

1) Light emitting diode (LED) is a two-lead semiconductor. It works by the principle of electroluminescence where when a sufficient voltage is supplied to the device electrons can recombine with electron holes within the device causing a release of photons, or light. They are often small but have long life-spans, are more energy efficient, and have less environmental concern attached to them. 2) Fluorescent lamps are low pressure mercury-vapor gas-discharge lamps that use fluorescence to create visible light. An electric current in the gas excites the mercury vapor which produces short-wave ultraviolet light that in turn cases a phosphor coating on the inside of the tube to glow. They are much brighter than incandescent lamps and more efficient; however, they have environmental concerns because of the mercury and they are not as bright or energy efficient as LED.

What reference standards, controls, and reference materials are there for FATM?

1) Reference standards: certified NIST traceable weights (balance and trigger pull), certified NISY traceable thickness blocks/gauges (digital micrometer), certified NIST traceable rulers (PFT and DSS), stage micrometer (digital measuring device) 2) Reference materials: ammunition components for annual performance verification on microscope 3) Controls: caffeine (negative in GSR), gunpowder (positive in GSR), nitrite swabs (positive in Modified Greiss)

How is a revolver different from a SA pistol?

1) Semi-automatic pistols have a chamber attached to the barrel as one integral piece of the firearm. A revolver uses a revolving cylinder that has multiple chambers which rotate into alignment with the barrel each time fir firearm is cocked. 2) Often time's revolvers may contain a fixed firing pin attached to the hammer as one piece. Semi-automatic firearms utilize a hammer or striker fire mechanism. 3) The main difference between a revolver and semi-automatic firearm is the way they are loaded and then cocked. For a revolver, the cylinder is manually loaded with cartridges. In order to cock a revolver, the hammer can either be manually pulled to the rear or in the case of a double-action revolver pulling the trigger will rotate the cylinder into alignment, cock the hammer, and then fire the gun. For semi-automatic pistol, a magazine is loaded with cartridges and inserted into the magazine well (grip) of the firearm. Pulling the action (slide) to the rear exposes the top cartridge and releasing the action will strip this cartridge from the magazine and chamber it. The process of loading the cartridge into the chamber also cocks the firing mechanism. When the trigger is pulled, the discharge of the projectile causes the action to be forced rearward against (under immense gas pressure from the combustion of the gunpowder), thus stripping and loading an unfired cartridge while cocking the gun again.

What is a comparison microscope and how does it work?

A comparison microscope is two compound microscopes each with its own objective(s), stage, and adjustments that is joined together with an optical bridge. A system of prism mirrors is used to bring the two images together in order to be viewed side-by-side through a single ocular, or binocular lens. A central prims mirror can be rotated in order to isolate the field of view to just one microscope. A compound microscope is one in which the magnification takes place in two stages; one lens (objective) enlarges the image and a second lens (ocular) further magnifies the enlarged image. With compound microscope, the objective creates a real image of the object and then the ocular lens treat the real image as an actual object and forms an enlarged virtual image of it.

What is the AFTE Theory of Identification?

1) The theory of identification as it pertains to the comparison of toolmarks enables opinions of common origin to be made when the unique contours of two toolmarks are in "sufficient agreement". 2) "Sufficient agreement" is related to the significant duplication of random toolmarks as evidenced by the correspondence of a pattern or combination of patterns of surface contours. Significance is determined by the comparative examination of two or more sets of surface contour patterns comprised of individual peaks, ridges, and furrows. Specifically, the relative height or depth, width, curvature and spatial relationship of the individual peaks, ridges, and furrows within one set of surface contours are defined and compared to the corresponding features in the second set of surface contours. Agreement is significant when the agreement in individual characteristics exceeds the best agreement demonstrated between toolmarks known to have been produced by different tools and is consistent with agreement demonstrated by toolmarks known to have been produced by the same tool. The statement that "sufficient agreement" exists between two toolmarks means that the agreement of individual characteristics is of a quantity and quality that the likelihood another tool could have been the mark is so remote as to be considered a practical impossibility. 3) Currently the interpretation of individualization/identification is subjective in nature, founded on scientific principles and based on the examiner's training and experience.

What does 7.62 x 39mm mean?

7.36x39mm is a caliber designation. The 7.63 represents the diameter measurement of the projectile, and the 39mm represents the case length measurement. This cartridge was designed and produced by the Soviets beginning in 1944 and is the cartridge employed by two of the most popular rifles in the world: AR-47 and SKS. The cartridge remained the Soviet standard until the 1970's when the 5.45x39mm cartridge was developed for the AK-47 rifle

Explain a disconnect. What type of firearm would use this?

A disconnector is a device that is intended to disengage the sear from the trigger. They are most commonly found in semi-automatic firearms and are designed to prevent full automatic firing (or runaways). It also prevents the gun from firing until it is in battery. They can also be found in manually operated firearms and are intended to prevent firing without pulling the trigger.

What is a firearm?

A firearm is a tool that utilizes the combustion of gunpowder and the subsequent gas pressure created to propel a projectile at a target. There are many variations and designs that exist, but all firearms are made to accomplish the same end goal.

Explain a firing pin block and a magazine safety.

A firing pin block is a passive safety (Internal) found in semi-automatic pistol designs. The firing pin block is intended to prevent the firing pin from striking the cartridge primer until the trigger is pulled. The trigger, usually through means of a trigger bar, has a piece that will depress a plunger, located on the slide, allowing for the firing pin to protrude through the aperture and strike the primer. Until the aforementioned plunger is depressed the firing pin is blocked from the aperture. A magazine safety is another passive safety on some firearms (semi-automatic handguns) that prevents firing unless the magazine is fully inserted into the firearm.

What is the ballistic coefficient?

A numerical value that can be calculated to assess a projectile's efficiency in flight to retain as much muzzle energy as possible. It is a proportion of the projectile's sectional density and its weight and can be calculated using the following equation: BC=M/(Cd A) BC=Ballistic Coefficient M=Mass Cd=coefficient of drag A=cross-sectional area The higher the ballistic coefficient is, the better the bullet's energy retention is.

Explain a rebound safety. What type of firearm would use this?

A rebound safety, or hammer rebound, is a safety mechanism generally found on revolvers. It is Defined by the AFTE Glossary as a safety features of some firearms wherein spring action retracts the hammer after it has struck the firing pin.

What is a revolver?

A revolver is defined in the AFTE Glossary as a firearm, usually a handgun, with a cylinder having several chambers so arranged as to rotate around an axis. The firearm is discharged successively by the same firing mechanism. Revolvers can be either single or double action. Single action requires the manual cocking of the hammer or striker where sufficient pressure on the trigger then releases the firing mechanism. Double action is a handgun mechanism in which a single pull of the trigger first cocks and then releases the hammer or striker.

Explain a sear block. What type of firearm would use this?

A sear block is a safety which blocks the release of the sear. If the firearm is in battery and is cocked, the sear is the piece connecting the trigger to the firing mechanism. The sear block (generally a thumb safety, or active safety) prevents the release of the sear and subsequently the gun from firing. Often times when the active safety is in the on position, the trigger will be blocked internally. A sear block safety can only be determined to be the active safety by taking the firearm apart in order to see what function the safety is preventing from happening.

What is semi-automatic firearm?

A semi-automatic firearm is a gun that is designed to fire a single projectile with each pull of the trigger. Different from a single shot rifle or revolver, semi-automatics utilize the gas pressure created from the burning of gunpowder in order to complete the cycle of fire. After pulling the trigger in a semi-automatic firearm, the gas pressure will unlock the breech and force the action of the firearm to the rear while simultaneously extracting and ejecting the fired cartridge case. Once the action is forced forward by the recoil spring it strips a cartridge from the magazine, feeds, and chambers the cartridge and then locks the breech (in blowback and delayed blowback pistol designs there is no mechanical locking of the breech). This also cocks the firing mechanism and connects the trigger with the sear so that the gun is ready to fire again with a pull of the trigger.

What is CMS?

A technique known as Consecutively Matching Striae (CMS) put forth by Al Biasotti and John Murdock, puts forth guidelines on how many consecutively repeated striated marks should be present on bullets for a conclusion of identification to be reached. This research was embarked upon after Biasotti evaluated over 720 known non-match bullets and noted that there was no instance where more than 4 consecutively repeated striated marks were present. Biasotti and Murdock's paper on the subject was published in 1997 and has been adopted by some laboratories throughout the community but is not a universally practice concept.

Explain a transfer bar safety. What type of firearm would use this?

A transfer bar is a safety mechanism usually found in revolvers. It is defined as an intermediary piece of metal which usually reciprocates with the trigger or hammer of a revolver to transfer the energy of the hammer to the firing pin. When the transfer bar is not in battery with the firing pin, the hammer cannot touch the firing pin. The AFTE Glossary lists the Ruger New Model single and double action revolver as firearms that utilize this type of safety.

Is ADFS an independent agency or is it affiliated with any other state/local law enforcement?

ADFS is an independent agency not affiliated with any law enforcement agency on the state or federal level. However, some ADFS employees are APOSTC certified having successfully completed training at one of the agency approved police academies.

What is a shotgun?

AFTE Glossary (pg. 107) defines a shotgun as a long gun designed to be shot from the shoulder, typically having a smooth bore and designed to fire shotshells. Shotguns and rifles both fall under the category of long or shoulder firearms, however a shotgun is differentiated by its smooth bore versus the rifled bore of a rifle. Some shotguns may possess rifling to be used with a slug, but there are still considered shotguns if the caliber designation of the firearm is a gauge. Shotguns can be either double-barrel (side-by-side or over/under) or single-barrel possessing many different actions. Shotguns also have a barrel constriction to restrict the spread of fired shot. This constriction is known as the choke and comes in many variations.

What is a carbine?

AFTE Glossary (pg. 29) defines a carbine as a rifle of short length and light weight originally designed for mounted troops. Specifically a carbine is a longer firearm that has a shorter barrel than a rifle or musket. The M4 carbine is a shorter and lighter variant of the M16A2 assault rifle, both of which are designed with the AR-15 platform. Some common carbines are the M4, AR-57, HK416E5, HKG36C, Hi-Point 995, M1, Mosin-Nagant line of carbines and SKS.

What is a pistol?

AFTE Glossary (pg. 85) defines a pistol as a handgun in which the chamber is integral with the barrel. The origin of the term possibly comes from the use of the saddle pommel used to carry /aim early hand cannons. The cavalry work for pommel is "pistallo." These hand cannons, the earliest type of hand-held firearm used, were muzzle loaded firearms used in Spain between the 13th and 14th centuries.

What is a rifle?

AFTE Glossary (pg. 98) defines a rifle as a firearm with a rifled bore designed to be fired from the shoulder. NIJ Module 8 (pg. 37) provides a range of calibers that can be seen in rifles as well as different action types and designs. It also provides a definition for the often misused term "assault rifle"; compact, select-fire, detachable box magazine-fed firearms that use a centerfire rifle cartridge and are designed primarily for military use. Many rifles resemble the true assault rifle, but they do not possess the selector and can only be fired in a semi-automatic mode.

Explain blowback operation. Give an example.

AFTE Glossary defines a blowback (simple) action as a design found in semiautomatic and automatic firearms where the weight of the bolt, the inertia of some component, and/or a mechanical delay is the main locking force and no mechanical locking of the breech occurs. These firearms directly utilize the breech pressure exerted on the head of the cartridge case to actuate the mechanism. The blowback (simple) action is generally employed on smaller caliber pistols that fire low pressure cartridges such as .22 rimfire, the .32 ACP, or the .380 ACP. One exception is Hi-Point who manufactures larger caliber pistols (.40 S&W and .45 ACP) that have the simple blowback design. These firearms possess an abnormally heavy slide in order to remain in order for the breech end of the firearm to remain closed long enough for the gas pressure to drop. In a sense, the blowback design is similar to the gas operation in that the cartridge case acts as the piston and is driven back against the breech face by expanding gas pressure. A delayed (retarded) blowback is defined as a system in which the breechblock is not locked but some mechanical delay is incorporated to ensure that the breechblock cannot move back with sufficient rapidity to allow the unsupported case to emerge from the chamber while the pressure is still high. Semi-automatic pistols that are chambered for the 9mm Luger and larger generally utilize a delayed blowback operation. These pistols have barrels that are not fixed to the frame and tip up when the action of the firearm is open. One of the main differences that sets the blowback operation apart from almost all other firearm operations is the fact that the breech is never actually locked.

Explain long-recoil. Give an example.

AFTE Glossary defines long-recoil as a system in which the bolt and barrel recoil a greater distance than the length of the unfired cartridge where the breech block is held to the rear while the barrel is driven forward by its own spring. When the barrel is fully forward it trips the catch thus releasing the breech block and loading the next cartridge. An example of a long-recoil firearm is the Browning Automatic shotgun (Auto-5) and the Remington Model 1100 shotgun

Explain short-recoil operation. Give an example.

AFTE Glossary defines short-recoil as a firearm mechanism (action) in which the breechblock remains locked to the barrel only while the pressure is high and involves a barrel travel of only about ½ inch. The locking device and the barrel then release and the two components separate. The barrel may wait on the return of the breechblock but in most modern designs, it is under spring tension and goes forward on its own into battery. Examples of short-recoil firearms would be 1911 style semi-automatic pistols in which the barrel has a set of locking lugs that hold it against the frame during the firing process until the pressure drops and the breech block moves to the rear to complete the cycle of fire.

What are subclass characteristics and an example?

AFTE Glossary: Features that may be produced during manufacturing that are consistent among items fabricated by the same tool in the same approximate state of wear. These features are not determined prior to manufacture and are more restrictive than class characteristics. Subclass characteristics may be exhibited in consecutively manufactured breech faces that were cut using the same broach, usually evident in the form of long continuous parallel lines that carry-over from one breech to the next.

What are individual characteristics and an example?

AFTE Glossary: Marks produced by the random imperfections or irregularities are produced incidental to manufacture and/or caused by use, corrosion, or damage. They are unique to that tool to the practical exclusion of all other tools. As the tool cuts the steel piece that is the barrel or breech face, chip formation occurs. As these tiny chips form and then subsequently break off, there are sudden stops and starts along the newly cut surface. Likewise, as this happens the tool begins to wear and change as it cuts. This constant combination of chip formation and tool wear creates a cut that is unique to a specific work piece and thus cannot be replicated.

What are class characteristics and an example?

AFTE Glossary: measureable features of a specimen which indicates a restricted group source. They result from design factors and are determined prior to manufacture. Class characteristics are the objective characteristics that are predetermined before manufacture of the tool. A firearm has class characteristics such as caliber, number of lands and grooves, direction of twist, location of ejector and extractor, and firing pin shape. Class characteristics are also associated with the machining of the firearm itself as the machining process that is going to be utilized will create a certain toolmark on the work piece when finished. If a breech face is broached, it will have parallel marks, but if it is milled, it may have circular or arced lines across the breech face.

What is AFTE?

AFTE is the Association of Firearm and Tool Mark Examiners and is a worldwide organization that facilitates the exchange of information and ideas as well as the development of methods and research throughout the firearms and toolmark identification community.

What is a stereo microscope and how does it differ from a compound microscope?

According to AFTE glossary, a stereo microscope is an optical instrument which provides three dimensional viewing of an objective through paired objectives and eyepieces; may share a common, main objective. The major difference is that a compound microscope has just one optical path divided at the observation tube to give the same image to both eyes. A stereo microscope has two separate optical paths, or axes, which allows for the depth perception and three dimensional views associated with the microscope. Also, compound microscopes have higher magnifications often in ranges of 40x to 1000x; a stereo microscope is often at a fixed magnification typically from 1x to 4x.

How often is your equipment checked for calibration?

All comparison microscopes and electronic balances that are used in casework are serviced annually by an ISO 17025 accredited vendor. Each day of use, all instruments undergo quality control and performance checks to insure they are functioning properly. Instruments such as the digital micrometer, PFT measuring device, etc. undergo maintenance on an as-needed basis.

Can you conclusions be scientific if your results are subjective?

Although conclusions in the field are subjective in nature, they are founded on validated scientific principles. Numerous validation studies that look at consecutively made tools produced by the same cutting tool have shown that each tool produced will leave unique marks on a work piece due to the random imperfections created during manufacture. Although there may exist some agreement between two substrates known to have been marked by different tools, the aforementioned validation studies have successfully proven that there exists a difference in the marks to determine that they were in fact not marked by the same tool but can still be identified back to the tool which did in fact mark them.

Explain active safety versus passive safety.

An active safety is one that can be engaged manually by the shooter. The most common active safety encountered is a thumb safety which can be manually operated by the shooter's thumb form on to off. A thumb safety generally acts as a trigger or sear block to prevent the gun from firing when in the off position. Other active safeties that could be encountered are a cross bolt safety, grip safety, and a sliding/tang safety. A passive safety is a design on the firearm that is in place (or on) until the trigger is pulled. This safety does not have to be manually actuated by the shooter. Examples would be a disconnect, drop safety, firing pin block, hammer block (transfer bar), and hammer rebound. Revolvers typically only have passive safeties.

How do you prevent making a misidentification via subclass characteristics?

An examiner must be away there is a potential for subclass characteristics to be present on the items being compared. To prevent misidentification, the examiner may look for individual random characteristics, minor imperfections and defects that are unique to that tool, rotate the object 90 degrees to look for individual marks that are present from motion against the tool in a direction away from the parallel lines.

What are the types of calibration checks used?

Daily Intermediate Checks (performed for the day of use) and Annual Intermediate Checks

Why is it important to be a member of an organization like AFTE?

Being a member of AFTE is important for examiners for various reasons. Membership provides examiners with access to resources such as the AFTE Journal, the forums, the GRC database and the annual AFTE conference. These are valuable resources both for collaboration with other examiners as well as educational opportunities to further one's knowledge in the field. It also gives the examiner a level of credibility and stature when testifying in court.

What is bullet wipe? What causes bullet wipe?

Bullet wipe is defined as the discolored area on the immediate periphery of a bullet hole, caused by the transfer of residues from the bearing surface of the bullet. These dark grey to black residues typically contain carbon, lead, bullet material, and possibly other constituents such as bullet lubricant and primer residues. Bullet wipe may occur at any range of fire. When a piece of clothing is tested using sodium rhodizonate, bullet wipe will appear as a pin color immediately around the entry hole and turn a purple/blue when HCl is later added.

Is CMS subjective or objective?

CMS can show some objective data in regards to the number of consecutively repeated striated marks seen on two bullets; however, a conclusion of an identification made based on CMS is still subjective. An examiner still has to determine how many CMS are present and whether or not it meets the requirements for an identification by physically looking at two bullets.

What is a caliber class? Give an example.

Caliber class is the umbrella that specific caliber designations fall under. It is a method that groups numerous different calibers together based on the diameter of the bullet. An example would be the 38 caliber class. The 38 caliber class has numerous different cartridges that fall under its umbrella including .38 Special, .257 Magnum, .357 SIG, .38 Auto, and 9mm Luger. All these cartridges possess bullets that have a base diameter measuring approximately 0.355" to 0.358". Other common caliber classes that are encountered in the laboratory are 22, 30, 32, 40, 45, and 50.

What are the three definitions of caliber?

Caliber is defined in three ways by the AFTE Glossary and are as follows: 1) A term used to designate the specific cartridge for which a firearm is chambered. 2) In firearms, caliber is the approximate diameter of the circle formed by the tops of the lands of a rifled barrel, typically expressed in hundredths of an inch (.38) or millimeters (9mm). 3) In ammunition, caliber is a numerical term, without the decimal point, included in a cartridge name to indicate the nominal bullet diameter.

What is the primary piece of equipment you use to compare bullets, caliber cartirdge, etc.?

Comparison microscope

Does every barrel possess different microscopic irregularities? How/why?

During the manufacturing process in order to create the bore that the bullet will travel down. The barrel begins as a barrel blank and is deep hole gun-drilled in order to create the inside bore. This is a rough process and must be smoothed over using a finishing process, generally either reaming or honing. This finishing process utilizes a cutting tool (rotating around its axis whiles also moving parallel to the bore's axis) that takes off a very small amount of metal at a time. As the tool cuts, a buildup of metal around the blade's edge will develop and gradually break off. This is known as chip formation and imparts uniqueness to that barrel. As the tool cuts, it is constantly changing due to ship formation and thus the tool will never produce the same cut on two consecutive barrels. Barrels will also develop unique characteristics due to fear and tear from repeated used as well as the abuse of the firearm itself.

Describe the scientific controls used in the testing/analysis which you use to assure the tests are performed properly.

Each instrument in the lab undergoes an annual performance verification using certified reference standards. These reference standards must be within the calibration dates noted on the certificate that accompanies the standard. Each instrument must be checked for the day of use using the certified reference standards. A log of all daily quality control instrument checks is kept in ChemInventory. Where applicable, internal reference materials will be used to insure the accuracy of test results. An example of this would be the positive and negative controls used for gunpowder analysis (chemical color test). Scientists must participate in an external and internal proficiency test each year for those test and analyses that they perform in the laboratory. All reports generated will be subject to a peer technical review to insure that two scientists independently come to the same conclusion before a final report is signed and mailed to the submitting agency.

What kind of identifying marks are left on expended cartridges?

Expended cartridges possess much more detail than bullets. On the head of the cartridge, more specifically the primer, impressed marks from the cartridge case's contact with the breech face during firing are visible. There is also a firing pin impression which can contain microscopic detail unique to a particular firearm. Other mechanical parts within a firearm such as the ejector, extractor, and chamber can leave identifying marks on a fired cartridge case as well.

Is FATM subjective or objective?

FATM has both subjective and objective analysis. When evaluating the comparison of toolmarks and whether or not those marks were produced by the same tool, the conclusion an examiner will reach is subjective. It is subjective because two different examiners can look at the same two items with the same toolmarks and come to different conclusions based upon what they see. Therefore, the conclusion an examiner reaches is his/her individual opinion about the toolmarks in question. When an examiner examines a fired bullet, the class characters such as caliber, direction of twist, and land/groove impression size are objective.

What is a Firearm and Tool Mark examiner?

First and foremost, a scientist, and as a scientist applies the scientific method to each case they work by understanding and implementing the four prongs of the aforementioned method. An examiner is also tasked with analyzing firearms and toolmarks related evidence submitted to the laboratory. The most important aspect of the examiner's job is comparing unknown fired ammunition components such as bullets and/or cartridge cases to known components from a suspect's firearm to determine whether there is sufficient individual characteristics to come to a conclusion. Examiner's understand and apply AFTE's Theory of Identification when making such comparisons.

What is forensic sciences?

Forensic science is defined in a broad sense by Saferstein in Criminalistics An Introduction to Forensic Science as the application of science to law. He further expands on this definition later stating that "Forensic science is the application of science to those criminal and civil laws that are enforced by police agencies in a criminal justice system.

What is GSR?

Gunshot Residue (GSR) is defined as the total amount of residues resulting from the discharge of a firearm. It includes gunpowder, primer residues, carbonaceous material, metallic residues from projectiles, fouling, and any lubricant associated with the projectiles. GSR is generally visible out to 3 to 4 feet in distance however this is not an absolute and is heavily dependent on the firearm and type of ammunition being used.

What is headspace?

Headspace is the distance from the face of the closed breech of a firearm to the surface in the chamber on which the cartridge case seats. It is a term that is very commonly confused with cartridge case head clearance which is defined as the distance between the head of a fully seated cartridge and the face of the breech bolt which the action is locked. Incorrect headspace for a given cartridge in a firearm can cause damage to the firearm and the shooter should the cartridge case rupture causing high pressure gas to vent from the breech of the gun.

What training do you have to qualify you in this area of forensic sciences?

I have a bachelor's degree from Troy University in Chemistry. I have also completed the modular training program set forth by the ADFS as well as the training manual developed by AFTE. My training has also included continued education in the field of firearms and toolmarks identification through various classes on the subject on the subject as well as tours of firearms manufacturing plants.

Can your matches be 100% certain? Explain.

Identifications are never 100% certain. Nothing in science is 100% certain and because an examiner cannot physically compare bullets fired in every gin in existence, there is always subjectivity attached to an identification. Likewise because the identifications are made by someone visually looking at the bullets and coming to their own conclusion, there exists the possibility that two independent examiners look at the same two bullets and come to different conclusions. Identifications are conclusions that are the opinions of the examiners doing the comparison and therefore cannot be made with 100% certainty.

What is the difference between a magazine and a clip?

Magazine and clip are two terms that are often incorrectly used interchangeably. AFTE Glossary (pg. 71) defines a magazine as a container for cartridges which has a spring and follower to feed cartridges into the chamber of a firearm. A clip is a device that can store multiple rounds of ammunition ready to be inserted into the magazine.

What are the Daily Intermediate Checks for the FTIR-ATR?

Maintained and checked by the Drug Chemistry discipline within the lab.

How does NIST apply to FATM?

Many of the standards that are used to perform daily quality control checks as well as those used to perform annual performance verification checks on the instruments are traceable back to NIST standards. Traceability back to a NIST standard fulfills one of the requirements set forth by ISO/IEC 17025_2005 pertaining to the calibration of reference standards used in the laboratory.

What type of powder is loaded in modern cartridges?

Modern cartridges are loaded with smokeless powder. There are many different types of smokeless powders such as single base, double base, and triple base, but all contain nitrocellulose.

What are some of the different morphologies of smokeless gunpowder?

Morphology refers to the size and shape of the individual gunpowder granules. The size and shape can affect the burn rate and directly control the rate of energy release. Some morphologies in smaller, low-pressure firearms are disk, flake, ball, flattened ball, and lamelle. These powder shapes burn quickly and do not produce the high pressure seen in rifle cartridges. The most common powder morphology seen in rifle cartridges is cylindrical, or tubular. This powder has much more surface area to burn and releases energy slower than the powders seen in smaller firearms. It burns in a more uniform manner creating a constant peak pressure.

What is NIST?

NIST stands for the National Institute of Standards and Technologies and is currently a part of the U.S. Department of Commerce. It provides the forensic science community as well as many other fields with standards of measurements and other technology. All reference standards utilized by ADFS are traceable back to a NIST standard.

Are you a ballistics expert?

No, the training that examiner's receive does not qualify them as an expert in ballistics; however, through other training and continued education examiner's may acquire knowledge in the field of ballistics sufficient to give an opinion on such matters in court.

Will a barrel always impart the individual characteristics onto a bullet?

No. Depending on the type of ammunition used, individual characteristics present in the barrel may or may not be imparted on the bullets. The cleanliness of the bore is another factor whether or not the bullet will possess uniqueness after traveling down the bore. Subcaliber ammunition fired in a larger caliber firearm could also lead to the absence of individual characteristics present in a barrel to be absent on the fired bullet.

Would you make a match on one individual marking that corresponds?

Numerous factors come into play when assessing whether one mark would be sufficient to make an identification. The tool marking the mark would have to be available for testing, the sample size would have to be large enough to show reproducibility, and the mark would have to be reproduced by the tool across numerous test media. Even still, whether the ultimate conclusion is an identification or not is completely up to the examiner conducting the examination. Where one examiner may see the mark as being sufficiently unique to make a determination, another examiner may feel there is insufficient microscopic detail to definitively determine.

If you don't use CMS, what method do you use?

Pattern matching is the most common method of comparing toolmarks used in the field. Pattern matching is defined in the NIJ Training Manual as "the process of determining whether or not the striated toolmarks on two objects, such as fired bullet, correspond."

What is the difference in a reference standard and a reference material?

Reference material is a material that has been established to be fit for the calibration of an instrument, the assessment of a measurement method, or for use in a measurement. These items are often times created within the laboratory and are not accompanied by a certificate that can trace the material back to a NIST or other certified standard. Reference standard is one that is accompanied by a certificate that traces that standard back to NIST or other certified known standards. This certificate also comes with an uncertainty associated with that standard.

What are the chemical components of black powder?

Saltpeter (KNO3), Charcoal (carbon), Sulfur. Composition varies depending on the reference, but according to Rinker (Understanding Firearm Ballistics pg. 22) black powder is made up of 14% Carbon, 10% Sulfur, and 76% saltpeter (typically a 15:10:75 ratio). Each component has a different role; the charcoal acts as the fuel, the saltpeter acts as the oxidizer and the sulfur acts as a catalyst.

What is science?

Science is the observation and understanding of the physical and natural world through experimentation of physical evidence. Experimentation follows the scientific method which has four major prongs: 1) Statement of hypothesis 2) Conducting the experiment 3) Gathering the data 4) forming a conclusion. FATM follows the scientific method in that the hypothesis that a trained examiner would propose is that due to the tool constantly changing during the manufacturing process (chip formation as the barrel/breech/etc. are cut) there exist microscopic imperfections in each manufactured component of a firearm. These imperfections impart individual characteristics not fired ammunition that are unique in a way so that the fired ammunition components can be identified back to a specific barrel/ breech/ etc. that possess those imperfections.

What are the Annual Intermediate Checks for the Balance?

Serviced annually by an approved provider using 6 NIST traceable weights to a 1% tolerance of the known value and 5% for 0.1 grain weight; weights included are 0.1, 1.0, 10.0, 100.0, 500.0, and 1000.0 grains

What are the Annual Intermediate Checks for the Comparison Microscope?

Serviced annually by an approved vendor; performance verification is accomplished through the comparison of a minimum of 2 known sample; identification by 2 scientists and photograph of the identification documented

What is the difference between a single action and double action firearm?

Single action firearms require the manual cocking of the hammer or striker before the firearm is ready to be discharged. Double action firearms both cock and fire the gun with a single pull of the trigger. Double action firearms can be DAO or DASA firearms depending on the gun model and manufacturer.

What is soot? Where does soot come from?

Soot, or smoke residue, is defined as the portion gunpowder residue which consists essentially of carbon and leaves a black deposit on a target surface when the muzzle of the firearm is very close to the target. A general rule of thumb is that soot is not observed on clothing after a distance range of 9 to 14 inches.

What is stippling? What causes stippling?

Stippling, or powder stippling, is defined as small hemorrhagic marks on the skin produced by the impact of gunpowder particles. Also used when referring to any small pits or defects in objects impacted by unburned and partially burned gunpowder particles. To be accurate from a medical point of view, the term stippling should be used when the marks are made on the surface of the skin by the grains without penetration. On inanimate objects, it is the creation of small pits or defects caused by the impact of unburned and partially burned gunpowder particles. Stippling is evidence of a relatively close range discharge of a firearm. According to Di Maio, stippling occurs at a muzzle to target distance of approximately 10mm.

What are striated and impressed marks and how are they different?

Striated toolmarks are created when a harder tool comes into contact with a softer work piece and there is motion approximately parallel between the tool and the work piece. An example of striated marks in firearms is those seen on the land impressions of fired bullets. As the bullet travels down the barrel, the harder steel of the bore scrapes against the bullet leaving striated marks. These marks created from the bullet coming into contact with the marks left from a finished process such as reaming or honing. Impressed marks are those created by a harder tool coming into contact with a softer work piece and imprinting a negative image of the tool into the work piece without the benefit of motion. Impressed marks are created when the tool strikes the work piece at a 90 degree angle. An example of an impressed mark is the breech face marks seen on a fired cartridge case.

What is tattooing? What causes tattooing?

Tattooing, or powder tattooing, is defined as the embedding of unburned and partially burned gunpowder particles in the skin or other tissue with accompanying hemorrhagic marks associated with living tissue. The term almost always applies to skin because skin is the surface, apart from clothing, through which bullets commonly enter the body. To be accurate from a medical point of view, the term tattooing should be used when the particles penetrate the skin.

Explain gas operation. Give an example.

The AFTE Glossary defines a gas operated firearm as an automatic or semi-automatic firearm in which the propellant gases are used to unlock the breech bolt and to complete the cycle of extracting and ejecting. A portion of the gas created from the burning of the propellant powder is vented from the barrel during firing into a chamber where a piston pushes against a spring. This spring resists the recoil energy against the breech face for an instant until the projectile exits the muzzle and the pressure drops to a safe level. This action is usually performed in conjunction with a spring that returns the operating parts to battery. Examples of gas operated firearms include the Remington Model 1100 shotgun, M1, M14, M16 and IMI Desert Eagle. The M16 utilizes direct impingement which is a type of gas operation for a firearm that directs gas from a fired cartridge directly into the bolt carrier or slide assembly to cycle the action. Direct impingement differs from conventional gas operated firearms in that is does away with the separate gas cylinder, piston and operating rod. High pressure gas acts directly on the bolt and carrier.

What is the AFTE Theory of Identification?

The AFTE Theory of Identification as it related to Toolmarks is defined in the AFTE Glossary as follows: 1) The theory of identification as it pertains to the comparison of toolmarks enable opinions of common origin to be made when the unique surface contours of two toolmarks are in "sufficient agreement." 2) "Sufficient agreement" is related to the significant duplication of random toolmarks as evidenced by the correspondence of a pattern or combination of patterns of surface contours. Significance is determined by the comparative examination of two or more sets of surface contour patterns comprised of individual peaks, ridges, and furrows. Specifically, the relative height or depth, width, curvature, and spatial relationship of the individual peaks, ridges, and furrows within one set of surface contours are defined and compared to the corresponding features in the second set of surface contours. Agreement is significant when the agreement in individual characteristics exceeds the best agreement demonstrated between toolmarks known to have been produced by different tools and is consistent with agreement demonstrated by toolmarks known to have been produced by the same tool. The statement that "sufficient agreement" exists between two toolmarks means that the agreement of individual characteristics is of a quantity and quality that the likelihood another tool could have made the mark is so remote as to be considered a practical impossibility. 3) Currently the interpretation of individualization/identification is subjective in nature, founded on scientific principle and based on the examiner's training and experience.

How do you determine shot size?

The Rule of 17 is a good method to approximate the size of shot; however, the FATM SOP for ADFS states that the shot size will be determined by first measuring both the diameter and weight of the shot then comparing those values to shot size reference tables or known standard. There is no protocol in place to use the Rule of 17 as a test method for analyzing shot size.

What is the rule of 17?

The Rule of 17 is a mathematical equation used to determine the size of shot. By subtracting the diameter of a shot pellet from the number 17, the value will give an approximate shot size. This equation can be manipulated to calculate for the diameter of a specific size shot. This rule only applies for standard U.S. size shot and will not work for buckshot.

Explain the review system in place at ADFS.

The Technical and Administrative review procedures are in the FATM SOP located on Qualtrax under sections 5.9.4 and 5.9.5 respectively. All conclusions of comparisons will be verified by a second scientist through direct evidence examination. Any disagreements between the verifying scientist and reporting scientist will be mediated by the Discipline Chief/Technical Leader and is needed will be the one to sign the report. A Technical and Administrative Review will be completed on ALL cases reported in FATM section by an approved scientist. The components of each review can be found in Qualtrax in the aforementioned sections. The Technical and Administrative reviews will both be documented in LIMS under the assignments tab for FATM as well as through routing codes.

What is forensic sciences?

The application of scientific techniques and testing to evidence recovered from a crime scene and the subsequent testimony in the justice system to defend and explain the results of the aforementioned analysis in a court of law. Where science and the legal system both intersect and interact.

Explain the cycle of fire.

The cycle of fire is explained in detail by the NIJ Firearm Examiner Training program module 8 (pg. 8). It is a 9 step process that is applicable to all breech loading firearm: 1) Feeding - a term connected with chambering it refers to the action of inserting the cartridge into the chamber. This can be done manually or through the use of a magazine. 2) Chambering - often connected with feeding this term refers to the actual insertion of the cartridge into the chamber. 3) Locking - this is where the breech bolt locks the cartridge into position (the chamber) before firing. This locking step is essential in that most firearms possess a safety mechanism, known as a disconnector that disengages the trigger from the firing pin until locking is accomplished. 4) Firing - depression of the trigger will trip the sear allowing the firing pin into strike the primer of the cartridge. Firing pin release is accomplished utilizing a striking the firing pin. Many semi-automatic pistols also possess a safety mechanism known as a firing pin block. This firing pin block prevents the firing pin from striking the primer until such time that the trigger is pulled and depresses a plunger that is blocking the path of the firing pin. 5) Obturation - priming powder ignites the main powder charge creating high pressure gases. The cartridge case is made from flexible material that will expand against the chamber wall sealing the breech end of the firearm. Likewise the bullet is manufactured to a diameter that is slightly larger than the bore diameter so that it extrudes into the grooves sealing the muzzle end of the firearm. This sealing causes the high pressure gases to exert an immense amount of force against the bullet and the cartridge case in opposite directions. During this step the firearm must remain locked until the chamber pressure had returned to zero, i.e. the bullet has exited the muzzle of the barrel. 6) Unlocking - when the chamber pressure returns to zero, the breech bolt will unlock allowing for extraction of the fired cartridge case and then ejection. 7) Extraction - fired cartridge cases are larger in diameter than before and thus have a tendency to stick to the chamber walls. A part known as the extractor has a claw that grips the groove at the head of the cartridge and pulls the fired cartridge case out of the chamber as the breech colt moves to the rear. 8) Ejection - as the extractor pulls the fired cartridge case out of the chamber another part known as the ejector, often located at right angles to the ejection port, comes in contact with the case and "kicks" the case out of the firearm. 9) Cocking - as the breech bolt completes its rearward motion and the fired cartridge case has been ejected the hammer spring is compressed, or cocked. On firearms with an exposed hammer, it will be pulled to the rear as an indication that it is ready to fire. Only when the breech bolt returns forward, loading a new cartridge into the chamber, and locks will the trigger be connected to the firing mechanism again.

Explain how a cartridge is fired or discharged.

The firing process of a cartridge begins with the firing pin strikes the primer crushing the priming powder against the anvil. The subsequent ignition of the priming powder sends a flame through the flash hole in the base of the cartridge and ignites the main powder charge. Once the main powder charge is ignited it will burn rapidly under very intense pressure due to the obturation occurring within the firearm form the bullet and the cartridge case sealing both ends. As the powder rapidly burns creating more gas and higher pressures, the force of the gases begins to push against the base of the bullet and the cartridge case. This force from the expanding gases accelerates the bullet down the barrel and simultaneously begins to push the breech block to the rear of the firearm. Ideally the powder in the cartridge will be completely burned before the bullet leaves the muzzle that there is no wasted energy, but not so soon as to lose energy before the bullet leaves the muzzle.

What kind of identifying marks are left on expended bullets?

The most common marks visible on expended bullets are striated marks from the bullet's passage down the barrel of the firearm, seen on the land and groove impressions on the bullet. The land and groove impressions themselves can aid in identifying whether or not a particular firearm could have fired a particular bullet. Other marks may be present due to the bullet coming into contact with foreign material after leaving the barrel.

What are the objectives lenses?

The objective lenses are those lenses closest to the object being viewed. They magnify the object creating a real enlarged image of the object which the ocular lens then further magnifies.

What magnification are normally used during examination?

The ocular lens used in the comparison microscopes at the ADFS is a 10x magnification but multiple objectives are utilized for different magnifications. The objectives used on the Leica UFM4 are 1x, 1.5x, 2x, 2.5x, 3x, and 4x. For casework the total magnification typically used is 10x and 20x although 40x is utilized some as well. The Leica FS C microscope has a 0.4x magnification that totals 4x that can be used when necessary.

What is smokeless powder composed of?

The primary component found in all smokeless powders is nitrocellulose. Nitrocellulose is the result of treating cellulose with nitric acid in the presence of sulfuric acid (NIJ Module 5 pg.9). The nitrocellulose is then dissolved in an alcohol-ether solution to make it stickier and more cohesive which is necessary for processing. Initially cotton linters were used as the source of cellulose but recently finely ground wood fibers have replaced linters as a source of cellulose. Double base powders contain nitrocellulose and nitroglycerin. Triple base powders contain nitrocellulose, nitroglycerin, and nitroguanadine. For double base powders, nitroglycerin acts as the nitrocellulose solvent rather than the alcohol ether solution. All gunpowder must possess 3 important characteristics traits: 1) When it burns, it produces a huge quantity of gas. 2) As it burns, it produces a huge amount of heat. 3) After ignition it creates its own oxygen and needs no outside air.

Explain a ¼ cock notch. What type of firearm would use this?

The quarter cock notch is another name for the safety notch. It is a safety mechanism found on some older revolvers to allow for carry of a loaded gun. With the hammer back in the quarter cock notch, the fixed firing pin could not reach the primer of an unfired cartridge. This safety mechanism was the subject of various accidents which pushed manufacturers to abandon the notch as a safety device all together and opt for more practical and effective mechanisms such as the hammer rebound and transfer bar. This is not the half cock which is the position of the hammer of a firearm when about half retracted and held by the sear, intended to prevent release of the hammer without normal pull of the trigger.

What do the terms "subjective" and "objective" mean? How are they different?

The term subjective pertains to a conclusion derived from an individual's thoughts, feelings, or opinions. In FATM, the conclusions drawn by an examiner are subjective in natures because they are the opinions of that individual examiner based on what is observed during the analysis of the tool marks. Objective relates to a conclusion that is founded on facts or measurement. If an examiner reaches a conclusion that is objective, it is based upon verifiable data that supports that conclusion and cannot be disputed.

How many matching/corresponding marks are required for an ID?

There is not standard number of matching marks that has to be met in order to call a comparison an identification. The conclusion of an identification (or exclusion, inconclusive) is subjective to the examiner making the determination. A technique known as Consecutively Matching Striae (CMS) put forth by Al Biasotti and John Murdock, puts forth guidelines on how many consecutively repeated striated marks should be present on bullets for a conclusion of identification to be reached. This research was embarked upon after Biasotti evaluated over 720 known non-match bullets and noted that there was no instance where more than 4 consecutively repeated striated marks were present. Biasotti and Murdock's paper on the subject was published in 1997 and has been adopted by some laboratories throughout the community but is not a universally practice concept.

What are a .357SIG and a .45GAP? How are they different?

They are two different caliber designations for use in semi-automatic pistol. The .357SIG was developed by SIG Sauer and Federal Cartridge in 1994 as a 38 caliber class bullet that could be fired in a semi-automatic pistol at a higher velocity than a 9mm cartridge and also mimic the performance of a 125 grain .357 MAG bullet. IT is loosely designed as a necked-down .40 caliber cartridge but in actuality is slightly longer than the .40 S&W caliber cartridge as 9x22mm. The .45 GAP (Glock Automatic Pistol), was designed by Ernest Dunham at CCI/Speer at the request of Glock in 2002. The case length is shorter than that of the .45 ACP but possess the same diameter. It's purpose was to provide as much power as the .45 ACP but have a stronger case head and be shorter in length in order to fit into more compact guns. To increase head strength the GAP has a small-pistol primer rather than the large-pistol primer seen in the .45 ACP cartridge. The .45 GAP magazines fit the same dimensions as the 9mm Luger, .40 S&W, and .357 SIG.

What are the Annual Intermediate Checks for the Digital Micrometer (calipers)?

Using NIST traceable measuring blocks/gauges that are 0.040, 0.105, 0.500, 0.710, and 1.000 inches thick to a tolerance of 1% of the known value.

What are the Daily Intermediate Checks for the Digital Micrometer (calipers)?

Using NIST traceable measuring blocks/gauges that is 0.105" thick; recorded value for day of use must be within 1% of .105" or ±.00105

What are the Annual Intermediate Checks for the Distance Standards System (DDS)?

Using NIST traceable rulers in lengths of 6, 12, and 24 inches

What are the Daily Intermediate Checks for the Distance Standards System (DDS)?

Using NIST traceable rulers in lengths of 6, 12, and 24 inches

What are the Daily Intermediate Checks for the TriggerScan?

Using NIST traceable standard weights in the amount of 1 and 20 pounds

What are the Daily Intermediate Checks for the Balance?

Using NIST traceable standard weights in the amount of 1.0 and 100.0 grains; measurements must be within 1% of the known value.

What are the Annual Intermediate Checks for the Digital Measuring Software?

Using a NIST traceable stage micrometer; 0.0.10, 0.050, 0.100, 0.250, and 0.400" used for annual verification and must be within ±0.003" inches of the known value.

What are the Daily Intermediate Checks for the Digital Measuring Software?

Using a NIST traceable stage micrometer; 0.100" for each day of use and must be within ±0.003" inches of the known value.

What are the Annual Intermediate Checks for the PTF Measuring Device?

Using barrel rods to NIST traceable rulers in lengths of 6, 12, and 24 inches; measurements are recorded to the nearest 1/16th of an inch and must be within a tolerance of ± 1/16".

What are the Daily Intermediate Checks for the PTF Measuring Device?

Using barrel rods to NIST traceable rulers in lengths of 6, 12, and 24 inches; measurements are recorded to the nearest 1/16th of an inch and must be within a tolerance of ± 1/16".

How can you say all tools are unique if you have not examined all the tools in the world?

Without examining every tool in the world, there is no way to say with 100% accuracy that every tool ever manufactured is unique. The science behind firearms and toolmark analysis has however been validated itself through numerous validation studies that show each tool manufactured has uniqueness. These studies are designed to look at components such as barrels, breech faces, etc. that are produced consecutively on a manufacturing line to show that consecutively manufactured tools, produced by the same tool, will still impart individual characteristics on a work piece because the tool that made them is constantly changing during the manufacturing process. This change in the tool that imparts random imperfections during the manufacturing process is due to a phenomenon known as chip formation and is a direct result of the tool working surface becoming worn and altered during its life span.

Is FATM a science?

Yes, FATM follows the scientific method and has been validated over many studies that show there is individuality attached to individual tools. Even though it has come under scrutiny recently, FATM has still shown reproducible results when analysis follows the scientific method correctly.

Is it possible for an analyst to make a mistake regarding conclusions for examinations conducted?

Yes, mistakes are a possibility due to the inherent subjectivity of conclusions regarding the comparison of two toolmarks. In an attempt to ensure the highest quality of work possible, a second examiner will thoroughly review the work and come to their own conclusion. If there is a disagreement pertaining to the comparison of the toolmarks then a third examiner will be brought in to evaluate the toolmark and reach their own conclusions as well. With this review process, mistakes can be detected and avoided but not completely eliminated. Nothing in science is ever 100% accurate and when dealing with a subjective conclusion mistakes are always a possibility. The ADFS FATM SOP 5.9.4 Technical Reviews and section 5.9.5 Administrative Reviews details the review process for examiners through the state.