ar firearms quality manual

8/18/2019 Ar Firearms Quality Manual

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Firearms & Tool Marks Section Quality Manual

Document ID: FA-DOC-01 Approved By: Executive Director/Scientific Operations Direc

Revision Date: May 6, 2010 Page 1 of 88

A R K A N S A S

STATE CRIME LABORATORY

F IREARMS & T OOLMARK

QUALITY M ANUAL

Executive Director:

Kermit B. Channell, II


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Section 1.0 Introduction................................................................................................................... 51.1 Organizational and management structure............................................................................ 5

Section 2.0 Personnel Qualifications and Training.......................................................................... 6

2.1 Job Description- See Employee History Binder ................................................................... 6

2.2 Educational Requirements .................................................................................................... 62.2.1 Chief Firearms Examiner.............................................................................................. 6

2.2.2 Firearms Examiner........................................................................................................ 6

2.2.3 Firearms Examiner Trainee........................................................................................... 62.3 Special Training Requirements............................................................................................. 6

Section 3.0 Facilities........................................................................................................................ 7

3.1 Security ................................................................................................................................. 7Section 4.0 Evidence Handling........................................................................................................ 8

4.1 Scope:.................................................................................................................................... 8

4.2 Classification: ....................................................................................................................... 8

4.3 Basis:..................................................................................................................................... 8

4.4 Procedures For Evidence Handling: ..................................................................................... 84.4.1 Evidence handling upon initial examination: ............................................................... 8

Section 5.0 Validation.................................................................................................................... 10Section 6.0 Analytical Procedures ................................................................................................. 11

6.1 Firearms Identification Protocols........................................................................................ 11

6.1.1 Physical Examination and Classification of Firearms ................................................ 116.1.2 Safe Firearm Handling................................................................................................ 12

6.1.3 Pre-Firing Safety Examination ................................................................................... 12

6.1.4 Trigger Pull Examination............................................................................................ 136.1.5 Barrel and Overall Length Measurement of a Firearm............................................... 16

6.1.6 Rusty Firearm Examination ........................................................................................ 176.1.7 Sound Suppressor Examination .................................................................................. 17

6.1.8 Malfunctioning Firearm Examination......................................................................... 18

6.1.9 Firearms Reference Library ........................................................................................ 21

6.1.10 Test Firing and Recovery of Test Fires....................................................................... 236.1.11 Downloading............................................................................................................... 25

6.1.12 Primed Cartridge Case/Shotshell ................................................................................ 26

6.1.13 Caliber Determination................................................................................................. 276.1.14 Measuring Land Impression and Groove Impression Widths .................................... 28

6.1.15 National Integrated Ballistic Information Network .................................................... 30

6.1.16 GRC Utilization .......................................................................................................... 326.1.17 Wadding Determination.............................................................................................. 33

6.1.18 Shot Determination ..................................................................................................... 34

6.1.19 Physical Examination & Classification of Fired Bullet/Slug Evidence...................... 356.1.20 Physical Examination & Classification of Fired Cartridge Cases .............................. 37

6.1.21 Physical Examination & Classification of Fired Shotshells ....................................... 38

6.1.22 Subclass Characteristics.............................................................................................. 39

6.1.23 Microscopic Comparison............................................................................................ 406.1.24 Trace Material Examination ....................................................................................... 41

6.2 Range Determination Protocol............................................................................................ 43




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6.2.1 Visual Examination..................................................................................................... 43

6.2.2 Microscopic Examination ........................................................................................... 446.2.3 Infrared (IR) Photographic Examination .................................................................... 46

6.2.4 Haemo-Sol Cleaning of Bloodstains........................................................................... 48

6.2.5 Diphenylamine Test .................................................................................................... 49

6.2.6 Modified Griess Test................................................................................................... 506.2.7 Sodium Rhodizonate Test ........................................................................................... 52

6.2.8 Dithiooxamide (DTO) Test......................................................................................... 54

6.2.9 Distance Determination Test Pattern Production........................................................ 566.2.10 Gunshot Residue (GSR) Pattern Without a Gun......................................................... 57

6.3 Tool Mark Identification Protocol ...................................................................................... 59

6.3.1 Examination and Physical Classification – Tool ........................................................ 596.3.2 Examination and Physical Classification – Tool Mark............................................... 60

6.3.3 Subclass Characteristics.............................................................................................. 60

6.3.4 Trace Material Examination ....................................................................................... 61

6.3.5 Test Standards............................................................................................................. 62

6.3.6 Microscopic Comparison............................................................................................ 636.3.7 Magnesium Smoking .................................................................................................. 64

6.3.8 Casting ........................................................................................................................ 656.4 Serial Number Restoration Protocol ................................................................................... 66

6.4.1 Serial Number Restoration.......................................................................................... 66

6.5 Fracture Match Protocol ..................................................................................................... 706.5.1 Fracture Match............................................................................................................ 70

6.6 Range of Conclusions ......................................................................................................... 73

6.6.1 Firearms Range of Conclusions .................................................................................. 736.6.2 Toolmarks Range of Conclusions............................................................................... 73

6.7 Work Sheets ........................................................................................................................ 756.7.1 Firearm Work Sheets: ................................................................................................. 75

6.7.2 Fired Bullet Work Sheet: ............................................................................................ 75

6.7.3 Discharged (Expended) Cartridge Case Work Sheet:................................................. 76

6.7.4 Firearms Worksheets .................................................................................................. 76Section 7.0 Calibration and Maintenance: ..................................................................................... 78

7.1 Calibration Standards.......................................................................................................... 78

7.1.1 Comparison Microscope: ............................................................................................ 787.1.2 Stereo Microscope: ..................................................................................................... 78

7.1.3 Measuring Projection Microscope: ............................................................................. 79

7.1.4 Stage Micrometer........................................................................................................ 797.1.5 Balances/Scales........................................................................................................... 79

7.1.6 IBIS / NIBIN............................................................................................................... 79

7.1.7 Trigger Pull Devices ................................................................................................... 797.1.8 Digital Caliper/ Dial Caliper....................................................................................... 80

7.1.9 Rectangular Gage Blocks (0.050 inches, 0.200 inches, 0.400 inches and 1.000

inches) 80

Section 8.0 Proficiency Testing: .................................................................................................... 82Section 9.0 Case Records............................................................................................................... 83

9.1 Examination Documentation .............................................................................................. 83




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9.2 Technical and Administrative Review................................................................................ 83

Section 10.0 Testimony Review .................................................................................................. 84Section 11.0 Audits...................................................................................................................... 85

Section 12.0 Complaints .............................................................................................................. 86

Section 13.0 Miscellaneous ......................................................................................................... 87

Section 14.0 APPENDIX............................................................................................................. 8814.1 Glossary .............................................................................................................................. 88

14.2 Abbreviations...................................................................................................................... 88




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Section 1.0 Introduction

The purpose of this Quality Manual is to establish general guidelines for the handling of firearms,

tool mark evidence, serial number evidence; the examination of firearms evidence, tool mark and

serial number evidence; the reporting of firearms, tool mark and serial number results; and theresponse to court commitments.

Goal

It is the goal of firearm examiners to insure the quality, integrity, and accuracy of the examination

and analysis of firearm and tool mark evidence through the implementation of a Quality AssuranceProgram and to:

1. Provide such services to law enforcement agencies, attorneys, and courts in criminal matters

in accordance with the policies of the laboratory.

2. Provide expert witnesses for criminal judicial proceedings in accordance with the policies of

the laboratory.

Objective

It is the objective of the Quality Assurance Program to:

1. Monitor, on a routine basis, the examinations and analyses of the firearms examiners by

means of quality control standards and proficiency tests.

2. Verify that all section protocols and procedures are within established performancecriteria, that the quality and validity of the analytical data are maintained and that the raw

data gathered provides a sound foundation for reliable conclusions.

3. Ensure that problems are noted and that corrective action is taken and documented.

1.1 Organizational and management structure

Refer to FA-DOC-03 for Firearms Section Organization & Management Structure




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Section 2.0 Personnel Qualifications and Training

2.1 Job Description- See Employee History Binder

2.2 Educational Requirements

2.2.1 Chief Firearms Examiner

The position requires a minimum of a four year degree from an accredited college or university witha major in forensic science, criminalistics, or in a physical or natural science and five years of

professional experience as a Firearms Examiner in a forensic laboratory.

2.2.2 Firearms Examiner

A four year degree from an accredited college or university with a major in forensic science,

Criminalistics, or in a physical or natural science and one year of professional experience as aFirearms Examiner in a forensic laboratory or identification division. In addition, completion of theAssociation of Firearms and Toolmark (AFTE) Training Program, The Arkansas State Crime

Laboratory Firearms Examiner Training Program or a comparable program from another forensic

laboratory or institution is required.

2.2.3 Firearms Examiner Trainee

Individuals with a four year degree from an accredited college or university with a major in forensicscience, Criminalistics or in a physical or natural science and a broad knowledge and background in

firearms is recommended.

2.3 Special Training RequirementsProfessional experience as a Firearms examiner in a recognized forensic laboratory, institution, or an

identification division may be substituted on a one year work time for one year of the requirededucational background. The individual must have testified as an expert in the field of Firearms

identification in a court of law.

An individual selected as a Firearms analyst trainee must be able to successfully complete the AFTE

Training Program, the Arkansas State Crime Laboratory Firearms Training Program or a comparable program from another forensic laboratory or institution is required.




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Section 3.0 Facilities

The Firearms section consists of six office areas, two microscope examinations room, GSR/Serial

number restoration room, tool room, bullet recovery room, indoor firing room, firearms reference

library and a NIBIN firearm processing room.

3.1 Security

Access to all of the office areas, microscope examination room, tool room, bullet recovery room,

indoor firing range and a NIBIN firearm processing rooms require a key for access twenty four hours

a day.

The firearm reference library is accessed by entry through evidence receiving where a log ismaintained regarding entry and exit.




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Section 4.0 Evidence Handling

4.1 Scope:

Evidence must be preserved to prevent significant change or alteration during the examination

through the completion of analysis. Evidence must be kept secure and the chain of custody must bemaintained once an examiner from the Firearms Section has assumed custody of that evidence.

4.2 Classification:

Items submitted or received through the use of a laboratory submission form will be treated as

evidence. Ammunition components which have been test fired through firearms for the purpose of

examination or entry into the NIBIN computer database will be identified and treated as referencematerial requiring the identification of the appropriate laboratory case number on the outside

package or inside information card.

4.3 Basis:

In order to maintain the security, chain of custody and to prevent change, all evidence must be stored

under proper seal, in the proper packaging and in a secure area.

4.4 Procedures For Evidence Handling:

Evidence will be checked out from Evidence Receiving in accordance with evidence policies.

4.4.1 Evidence handling upon initial examination:

• Be aware of all the sections and testing that involves the evidence. Take the necessary

precautions to preserve the integrity of the evidence.

• Descriptions of evidence containers, sealing, initials (this includes both outer and inner packaging) and evidence that is to be examined will be recorded in the case notes. Any

discrepancies should be noted.

• When evidence containers are opened for examination, opening through the seals of other

individuals who handled the evidence should be avoided, if at all possible.

• When evidence containers are opened for examination, the contents should be inventoried.This inventory should be matched to the Crime Laboratory Submission Sheet.

• Discrepancies shall be noted in the examiner’s notes. If deemed necessary, the submitting

officer or agency will be notified. All case-related communication will be documented on anASCL-FORM-06 Agency Contact Form.

• Evidence in progress may be stored in lockable cabinets, the tool room, the GSR/Serial

number restoration room, and the ammunition storage room. Evidence must be kept in oneof these locations for overnight storage.

• Each piece of evidence or its most appropriate proximal container must bear the followingidentifiers:




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1. Laboratory number (e.g. YYYY-000000)

2. Laboratory (section) Item number

3. Examiner’s initials

• If reusing the original container is impractical, a new evidence container may be used. It

shall also be marked and sealed according to laboratory procedures and the original evidence packaging shall be maintained, either inside the second evidence container or complete

documentation along with a picture of original packaging. Documentation of the change in

packaging along with description must be entered into the case file for future reference.

• The evidence will be returned to Evidence Receiving in a timely manner after completion.

• All pertinent information about the evidence will be recorded in the examiner’s notes. Casedocumentation must be sufficient to allow a technical peer review to be conducted.




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Section 5.0 Validation

• Refer to ASCL Lab Wide Quality Manual




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Section 6.0 Analytical ProceduresIntroduction

This section provides standard procedures for tests and examinations performed by the forensic

firearms and tool marks examiner. These procedures may involve hazardous materials, operationsand equipment. These procedures do not purport to address all of the safety problems associated

with its use. It is the responsibility of the user of these procedures to establish appropriate safety and

health practices and determine the applicability and normal limitations prior to use. Proper cautionmust be exercised and the use of personal protective equipment must be considered (see ASCLHealth and Safety Manual for safety requirements). Personal protective equipment includes, but is

not limited to: lab coats, latex or nitrile gloves, safety glasses, and hearing protection devices. The

examiner must consider the practicality and/or desirability to wear some form of bullet resistant

clothing. Proper caution should include strict adherence to the ASCL Health and Safety Manual.

6.1 Firearms Identification Protocols

6.1.1 Physical Examination and Classification of Firearms

• Other Related Procedures

o Safe Firearm Handling

o Pre-Firing Safety Checks

o Trigger Pull Examination

o Barrel and Overall Length Measurements

6.1.1.1 PROCEDURE or ANALYSIS

•

The initial examination of any firearm will include the completion of a firearm worksheet.This worksheet will include the manufacture data, if available, of the firearm and will serve

as a source to document the condition of the firearm as received and any tests performed toor with the firearm.

• The firearm worksheet may also include determining the following when appropriate:

o Location and type of trace evidence

o Caliber/Gauge

o Make/Model

o Serial Number

o Firing Mechanics

o Type of Action

o Safeties

o Operating Condition

o Trigger Pull




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o Rifling Characteristics

o Barrel Length

o Overall Length

o Any other data as per Appendix 4.

6.1.2 Safe Firearm Handling

Firearms evidence in the laboratory environment must be handled correctly and treated with respect.

Occasionally, loaded firearms are received in evidence for a particular examination. These, of

course, need very special handling. All firearms must be treated as though they are loaded. Thisrule cannot be over stressed and must be followed at all times, whether it’s in the evidence receiving

area, firearms section, test firing area or in court. Safe firearm handling within the laboratory

environment corresponds with safe firearm handling in general. The only way to prevent accidentsis to practice safety at all times.

• OTHER RELATED PROCEDURES

o

Physical Examination and Classification of Firearms

o Pre-Firing Safety Checks

o Trigger Pull Examination

o Barrel and Overall Length Measurements


• The muzzle of the firearm must always be pointed in a safe direction.

• Prior to any examination, regardless of which section is receiving the firearm, a competent

individual must ascertain the loaded or unloaded condition of the firearm. This process must

be accomplished before the firearm is received by the laboratory.

• Test firing or any examination of the firearm that utilizes live ammunition, or a liveammunition component, will only be performed in designated test firing areas.

• A firearm will not be placed in the evidence vault or returned to any agency in either a loadedcondition or prior to its loaded or unloaded condition being checked.

6.1.2.2 REFERENCES

• “A Guide to Firearms Safety”, A Safety and Educational Publication of the National RifleAssociation, May 1994.

•

“Technical Protocols for the Handling of Firearms and Ammunition”, FBI, June 1992.

6.1.3 Pre-Firing Safety Examination

It is the responsibility of the firearm examiner to ensure that all appropriate safety function checks

are performed on a firearm or item of ammunition prior to test firing. The following is a list ofsafety checks, which shall be considered. The examiner must be mindful that individual case

situations may require a more extensive function test process than that which is listed here.




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• Deciding whether or not a firearm can be safely test fired from the normal hand held position

o Is the chamber/bore clear?

o Are there any signs of cracks or weaknesses in major parts of the firearm; such as theframe, slide or barrel?

o Does the firearm function, lock-up or dry fire as you would expect it to?

o Is the correct ammunition being utilized?

• Is it appropriate to utilize the evidence ammunition?

o Are there signs of reloading? If so, reconsider the need to test fire the evidence

ammunition.

o

Are there splits in the cartridge case neck and/or other significant damage to the

cartridge case?

o Is the ammunition of the correct caliber? This assessment of caliber cannot be based

on the head stamp!

o Are there existing toolmarks on pertinent surfaces of the ammunition?

o Is the ammunition needed for other tests; i.e., range determinations?

• Muzzle Loaders.

o Does the chamber/barrel appear sound?

o

Do the percussion nipples have oversize flash holes?

o If a black powder firearm is received in the loaded condition, it must have the bulletand charge removed. It may then be properly loaded prior to test firing.

o Is this an "original" muzzleloader or a modern reproduction? "Originals" must

always be remote fired.

6.1.3.2 INTERPRETATION OF RESULTS:

If any of the above considerations cannot be answered with a clear "yes" or otherwise rectified and

test firing is necessary, that firearm must be remote fired.

6.1.4 Trigger Pull ExaminationTrigger pull is defined as the amount of force, which must be applied to the trigger of a firearm to

cause sear release. This examination can provide vital information regarding the mechanical

operating condition of the firearm. The trigger pull of a firearm can be obtained utilizing standardtrigger weights, which make contact with the trigger at a point where the trigger finger would

normally rest.





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o Physical Examination & Classification of Firearms


• INSTRUMENTATION

o Standard Trigger Weights

o

Spring Gauge


The trigger pull examination normally is conducted after the firearm has been successfully test fired.

There is a remote possibility that the firearm may be damaged during this examination.

• SINGLE ACTION TRIGGER PULL WITH STANDARD TRIGGER WEIGHTS

o Insure that the firearm is unloaded.

o Cock the firearm.o Hold the firearm with the muzzle vertical.

o

Rest the trigger hook of the standard trigger weight hanger on the trigger where theaverage finger would normally rest, making sure it is not touching any other part of

the firearm, with the weights hanging parallel to the bore of the firearm.

o Add the weights until the sear releases.o Check two or three times, resetting the sear connection after each attempt. Record the

heaviest weight at which the sear will hold and not release. Record the lightest

weight necessary to cause consistent sear release. This will be the trigger pull range.

Note any revolver cylinder chamber that alters the trigger pullo It should be noted that measuring the trigger pull of a rimfire firearm should not be

performed on an empty chamber. A “dummy” cartridge should be used. The

examiner must also take into consideration the potential for damage of a centerfire

firearm and may wish to use a “dummy” cartridge in this instance as well.• DOUBLE ACTION TRIGGER PULL WITH STANDARD TRIGGER WEIGHTS


o Hold the firearm with the muzzle vertical.

o Rest the trigger hook of the standard trigger weight hanger on the trigger where theaverage finger would normally rest, making sure it is not touching any other part of

the firearm, with the weights hanging parallel to the bore of the firearm.

o Add weights until the weights pull the trigger through the double action sequence andthe sear releases.

o

Check two or three times, resetting the sear connection after each attempt. Recordthe heaviest weight at which the sear will hold and not release. Record the lightest

weight necessary to cause consistent sear release. This will be the trigger pull range. Note any revolver cylinder chamber that alters the trigger pull.

o It should be noted that measuring the trigger pull of a rimfire firearm should not be





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examiner must also take into consideration the potential for damage of a centerfire

firearm and may wish to use a “dummy” cartridge in this instance as well.

• SINGLE ACTION TRIGGER PULL WITH SPRING GAUGE


o

Cock the firearm.

o Hold the firearm with the muzzle parallel to the spring gauge.

o Insure the Spring Gauge indicator is “zeroed”.

o Rest the trigger hook of the Spring Gauge on the trigger where the average finger

would normally rest. Make sure it is not touching any other part of the firearm and

the Spring Gauge is parallel to the bore of the firearm.

o Apply pressure to the Spring Gauge, until the sear releases.

o Check two or three times, resetting the sear connection after each attempt.

o

Record the lightest weight(s) necessary for sear release.o Note any revolver cylinder chamber that alters the trigger pull.

o It should be noted that measuring the trigger pull of a rimfire firearm should not be


examiner must also take into consideration the potential for damage of a centerfirefirearm and may wish to use a “dummy” cartridge in this instance as well.

• DOUBLE ACTION TRIGGER PULL WITH SRING GAUGE


o Hold the firearm with the muzzle parallel to the spring gauge.

o

Insure the Spring Gauge indicator is “zeroed”.

o Rest the trigger hook of the Spring Gauge on the trigger where the average finger

would normally rest. Make sure it is not touching any other part of the firearm and

the Spring Gauge is parallel to the bore of the firearm.

o Apply pressure to the Spring Gauge, until the sear releases.

o Check two or three times, resetting the sear connection after each attempt.

o Record the lightest weight(s) necessary for sear release.

o Note any revolver cylinder chamber that alters the trigger pull.

o

It should be noted that measuring the trigger pull of a rimfire firearm should not be performed on an empty chamber. A “dummy” cartridge should be used. The

examiner must also take into consideration the potential for damage of a centerfirefirearm and may wish to use a “dummy” cartridge in this instance as well.


The results acquired are only an approximation and a different technique may lead to a different

trigger pull weight. The trigger pull is normally recorded to the nearest ¼ pound weight increment.




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6.1.4.3 REFERENCES

• Gamboe, Tom, "MAFS Firearms Workshop: Trigger Pull Methods," AFTE Journal, Vol. 18, No. 3, p. 77.

• Rios, Ferdinand and Thorton, John, "Static vs. Dynamic Determination of Trigger Pull,"

AFTE Journal, Vol. 16, No. 3, p. 84.

6.1.5 Barrel and Overall Length Measurement of a Firearm

Barrel length is defined as the distance between the end of the barrel and the face of the closed breechblock or bolt for firearms other than revolvers. On revolvers, it is the overall length of the

barrel including the threaded portion within the frame. Barrel length normally should include

compensators, flash hiders, etc., if permanently affixed. Overall length of a firearm is defined as thedimension measured parallel to the axis of the bore from muzzle to a line at right angles to the axis

and tangent at the rearmost point of the butt plate or grip. Removable barrel extensions, poly

chokes, flash hiders, etc., are not part of the measured barrel length or overall length. Care must betaken if any object is placed down the barrel to help expedite the measurement. Only a non-marring

item may be placed down the barrel, and only after all other tests are performed.



• INSTRUMENTATION

o Ruler (and/or)

o Tape Measurer (and/or)

o Non-marring Dowel


6.1.5.1.1 BARREL LENGTH

6.1.5.1.1.1 REVOLVERS:

• Measure the distance from the breech end of the barrel to the muzzle, excluding the cylinder.This measurement can be done directly or by placing a non-marring item down the barrel,

marking the distance from the breech end of the barrel to the muzzle and measuring this item.

• This measurement will be recorded in inches.

6.1.5.1.1.2 FIREARMS OTHER THAN REVOLVERS:

•

Measure the distance from the breech face in a closed and locked position to the muzzle.This measurement can be done directly or by placing a non-marring item down the barrel,

marking the distance from the breech end of the barrel to the muzzle and measuring this item.

• This measurement will be recorded in inches.

6.1.5.1.2 OVERALL LENGTH:




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Measure the distance from the butt to the muzzle. Measurement shall be made parallel to the bore

and recorded in inches.

• INTERPRETATION OF RESULTS:

o Measurements obtained should be considered only approximations based on the

device used to obtain the measurements.

6.1.5.2 REFERENCES

• “The Proper Method for Measuring Weapons”, AFTE Journal, Vol.14, No. 3, p. 10.

6.1.6 Rusty Firearm Examination

Rusty firearms or those found in water, etc. may be submitted for examination. Immediate attention

must be given to these firearms to prevent further damage to the firearm. The examiner should

instruct an agency recovering the firearm in a fluid such as water, to submit the firearm in a

container of the fluid. If this is not practical, the agency can be instructed to immediately and

thoroughly spray the firearm with a water-displacing product such as WD-40® or other similar

product to prevent further deterioration. It should be noted that the firearm might be too rusted to befunctional. Any firearm that cannot be unloaded must be examined in an area designated for firing

firearms (preferably a range).




• An examiner must take all necessary steps to insure that the firearm is unloaded. If it cannot be readily verified to be unloaded it must be examined in an area designated for the firing of

firearms. Determining whether or not a firearm is unloaded may necessitate a completedisassembly or in some cases, destruction (e.g. cutting)

• The examiner must determine to what extent restoring the firearm is necessary (i.e., for test

firing, for recovering manufacturer information, serial number, etc.).

• Soak the firearm in penetrating oil, de-rusting solvents or similar material.

• Periodically check the firearm until the firearm functions, or the desired information isrecovered. Clean the firearm with gun cleaning solvent, cleaning patches and cloth. Care

must be taken if any object is placed down the barrel. Only a non-marring item should be

placed down the barrel.

6.1.6.2

REFERENCES • Denio, Dominic, "Making a Rusted Gun Functional," AFTE Journal, Vol. 13, No. 3, p. 29

6.1.7 Sound Suppressor Examination

A silencer or sound suppressor is any device attached to the barrel of a firearm designed to reduce

the noise of discharge. Silencers can be commercially produced or homemade. They are typicallytubular metal devices, but may vary in shape or form.




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• Examine device to determine if it is, or is characteristic of, a silencer or sound suppressiondevice.

• Examiner will document and record his/her findings.

• After an initial examination, a report can be issued that the device is, or is characteristic of, asilencer or sound suppression device.

• Testing of a firearm and firearm/silencer combination must be conducted in an appropriate

setting, usually a range.

• In many instances the noticeable reduction in sound between the firing of the firearm with

the device attached vs. the firing of the firearm without the device is sufficient to determinethat the device is a sound suppressor.

6.1.7.2 REFERENCES

• Silencers - A Review And A Look At The State Of The Art," AFTE Journal, Vol. 23, No. 2, p. 668.

• Crum, Richard A. and Owen, Edward M., "Silencer Testing," AFTE Journal, Vol. 21, No. 2, p. 433.

6.1.8 Malfunctioning Firearm Examination

A firearms examiner may be called upon to examine a firearm to determine if the firearm willmalfunction. Many of these cases will deal with the question: "Will the firearm fire without pulling

the trigger?" In these instances it should be the goal of the examiner to acquire a detailed account of

the incident by thoroughly examining and testing the firearm. Examinations may include externaland internal observations, or striking or dropping the firearm in attempts to duplicate the incident as

reported. The examiner should attempt to conduct his/her examinations in a manner so as not to

alter the firearm. However, there may be occasions when damage may occur. Any change to thefirearm must be specifically documented in the examiner’s notes.



o

Primed Cases


No one procedure can sufficiently outline the steps necessary to examine all firearms for anymalfunction. However, the following list of examinations should serve as a guideline for the

examiner.

• Physical Check (Condition of Firearm as Received):




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o Cocked/Uncocked

o Safety position

o Loaded/Unloaded

o Cartridge Position

o

Stuck Cartridges/Discharged Cartridge Cases

o Presence and/or location of flares

• Visual Abnormalities:

o Barrel (loose, etc.)

o Receiver (condition)

o Slide (condition)

o Parts broken or missing especially:

The firing pin

The ejector or

The extractor

o Screws (loose or missing)

o Alterations or adaptations

o Sights

o Action (External)

Relationships of the action parts

o

Correct assembly The proper locking of the action on closing

Cylinder rotation (securely locks)

Hand relationship to the ratchet (worn)

Trigger pull (single action, double action) and striking of hammer.

o Safeties: (Drop hammer several times to check below safeties.)

¼ , ½ , Full Cock, Seating check (any false seating positions, pull off/push off,

etc.)

Grip, magazine, disconnector: function Thumb/Finger – note positions when firearm will fire

Rebound hammer or inertia firing pin

Position of the slide or bolt in order to fire

Condition of safeties

o Action Check




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o Check feeding

Magazine

Carrier or lifter

Feed Ramp

Magazine lips, etc.

o Slamfire

Extractor and/or Ejector markings on evidence cartridges/discharged cartridgecases

Unusual marks exhibited on the cartridges/discharged cartridge cases.

Check for any inherent “quirks” known about the particular firearm based on

literature or case data.

o Test Fire Firearm (note operation, misfires, etc.):

Note any operational problems

Ammunition involved (proper cartridge, type, reloads, etc.).

Check consistency of the impression on test and evidence.

• Special Situational Tests:

• Care should be exercised when the force to be used in testing could alter or damage internal parts and their working relationship(s). Damage caused by the examiner may prevent the

examiner from determining the cause of the reported malfunction.

• Action (Internal)

o

Hammer Notch(s) Worn

Burrs

Dirt, etc.

o Sear

Worn

Broken

Burrs, etc

o

Safeties (relationships and general parts relationship)

Broken

Altered,etc

Signs of any tampering or faulty assembly.




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6.1.8.2 REFERENCES

• Thompson, Roger C., "Firearms Malfunction Worksheets," AFTE Journal, Vol. 15, No. 1, p.100.

• American National Standards Institute, Inc., “American National Standard Voluntary

Industry Performance Standards Criteria for Evaluation of New Firearms Designs UnderConditions of Abusive Mishandling for the Commercial Manufacturers”. (ANSI/SAAMI

Z299.5-1985), November, 1985.

6.1.9 Firearms Reference Library

A Firearms Reference Library, File or Collection is maintained by the laboratory for various

scientific reasons, to include:

• To identify the make, model and source of evidence firearms.

• To provide exemplar firearms for various scientific testing purposes which might otherwise

compromise an evidence firearm.

•

To provide an exemplar resource for training new forensic scientists/evidence technicians or

in developing new technology for the scientific examination of firearms.

• To provide a source of firearms parts for the temporary repair of evidence firearms for test-

firing purposes.

• To provide a resource for the identification of firearms parts recovered at a crime scene.

• To provide a resource for the location and style of firearm serial numbers.



o

Ammunition Reference Collection


A Firearms Reference Library must be maintained under strict regulations and controls. Firearms,

which are deemed unsuitable for scientific purposes, should be verifiably destroyed. The laboratory

assumes all responsibility for security, control and destruction of these firearms.

A written record should be made immediately upon receipt of a firearm, intended for the reference

collection, in a “FIREARM LOG”. This entry should initially include;

• the log number assigned.

•

the date received.

• the submitting agency or source of the firearm.

• the receivers initials.

The “FIREARM LOG ” may be produced electronically by spreadsheet. The following data

columns may be used in the firearm log books. It is suggested that these columns be kept in thesame order as listed below with the log number being the first entry on the left side of the

spreadsheet.




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• LOG NUMBER:

o Assigned by the receiving laboratory at the time of receipt of the firearm.

• DATE RECEIVED:

o Date received at the laboratory.

• AGENCY or SOURCE:

o The agency or person transferring control of the firearm to the laboratory.

• CALIBER:

o Caliber or gauge of the firearm.

• MANUFACTURER:

o Make, brand and manufacturer, if known.

• MODEL:

o

Model number(s) and/or name.• TYPE:

o Type of action.

• FINISH:

o Finish on firearm.

• BARREL LENGTH:

o The barrel length of the firearm.

• SERIAL NUMBER:

o

The serial number as stamped on the firearm. “NONE” if the serial number does notexist or cannot be found. OBLIT if the serial number has been obliterated.

• COMMENTS:

o Notes regarding transfers, destruction, location case numbers, etc.

It is recommended that a receipt be issued for every firearm received for the reference library or

destruction utilizing a standardized form. The respective log number assigned to each firearm

should be recorded on this form. These forms should be maintained in some reasonable order.

Firearms reference library should be displayed and maintained in such a manner as to prevent thefirearms deterioration and to facilitate their inventory, safety and control.

All firearms received for reference or disposal should have their assigned log number inscribed on

the frame and/or receiver. Furthermore, all firearms placed in the reference library should be tagged

in such a manner so as to display that firearm’s location within the collection.

It is recommended that a system, whether it be a card file, or a computer data base also be

maintained. This will facilitate cross-referencing the collection between various fields.




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Great care must be given if the section decides to maintain only a computer database. The historical

archive that a Log provides and the difficulty to alter records within a Log must be considered.

6.1.9.2 REFERENCES

• AFTE Glossary, 3rd Edition

6.1.10 Test Firing and Recovery of Test Fires

In order to perform a microscopic comparison of a submitted firearm, a minimum of two (2) test

shots should be fired and recovered. Recovery methods include the water tank, and the cotton waste

recovery box. The type of firearm and ammunition tested will usually dictate the type of recovery

method used. The water recovery tank is usually used to recover bullets from handguns, rifles andslugs fired from shotguns. The cotton waste recovery box is usually used to recover bullets from

handguns, rifles and slugs fired from shotguns. The indoor firing range is usually used to test fire

firearms when the recovery of the fired projectile(s) is not necessary. One should be aware of themaximum velocity of the projectile that can be fired into a particular water tank, as well as the

proper water depth needed for firing. One should be aware of the maximum velocity of the

projectile that can be fired into a particular cotton waste recovery box.



o Downloading

o Primed Cases

MINIMUM ANALYTICAL STANDARDS and CONTROLS

Test fired bullet and cartridge case samples are to be treated as reference material only. If a

test fired bullet/cartridge case is used for comparison purposes at a later date, it will be documented

on the examiner’s report as being a reference bullet/cartridge case previously test fired in the firearmand retained at the Arkansas State Crime Laboratory.

o Test fire reference collections will be maintained in a secure area accessible by

Firearms Section personnel. Archived material will be stored in a secure area in the

ASCL Annex.


• A test fire information card will be filled out to include the ASCL case #, item # and

identifying information (if available) for the test firearm. The test fire information card will

be stored with the test fired bullets and cartridge cases.

•

The examiner should consider marking the bullet and cartridge case of each test shot withthe;

o Full or abbreviated laboratory case number and

o Full or abbreviated item number and/or

o examiner's initials.




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• If the examiner does not, or is unable to, mark the test fired bullet/cartridge case with theabove information, then the package containing the test fires and information card will be

sealed and initialed.

• The examiner should consider indexing and sequencing each shot and perform these

functions if necessary.

• Proper hearing and eye protection must be worn.

• Ensure that the Exhaust fans or system is turned on.

• Ensure all warning systems are activated.

• The examiner should consider the number of cartridges being loading into the firearm duringthe initial testing of the firearm.

• Ejected discharged cartridge cases must be retrieved.

• For Water Tank Recovery

o

Ensure that the water level is appropriate.o Ensure that all lids or doors of the water recovery tank are closed and properly

secured.

o Fire the firearm through the shooting port. If the firearm is capable of firing bothsingle and double action modes, a minimum of one (1) shot per mode should be

obtained.

o Recover the bullets using the vacuum tube.

• For Cotton Waste Recovery Box

o The examiner should consider wetting the first section of cotton in the box.

o

The examiner should consider the placement of paper partitions at various points in box to ensure tracking of the test shot, as well as insuring that the cotton is packed

down so as not to retain previous bullet paths.

o Ensure that all lids or doors of the box are closed and properly secured.

o Fire the firearm through the shooting port. If the firearm is capable of firing both

single and double action modes, a minimum of one (1) shot per mode should beobtained.

o Bullets should be recovered by searching through cotton, using partitions as guides.

• For Indoor Firing Range

o

If the firearm is capable of firing both single and double action modes, a minimum of

one (1) shot per mode should be obtained.

o The examiner should check the range to make sure no materials are left behind.

• For Remote Firing

o Set up the chosen remote firing device, as per guidelines set forth by the

manufacturer, in front of the appropriate recovery system.




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o Place firearm in device. It is recommended that the examiner first dry-fire the firearm

in the remote firing device before using live ammunition.

o Activate the remote device while standing behind a protective shield or whilestanding at a safe distance away from the firearm.

o Obtain fired tests.

6.1.10.2 REFERENCES

• Newquist, Andrew M., “New Bullet Recovery System”, AFTE Journal, February 1973, p.9.

• Molnar, S., “A Novel Bullet Recovery Method”, AFTE Newsletter, 16, p.17.

• Operators Manual, Water Recovery Tank, CyberNational Inc.

• “Bullet and Cartridge Case Recovery”, AFTE Journal, Vol. 16, No. 2, p.75.

• McBrayer, William S., "What? Another Water Tank and Bullet Stop!", AFTE Journal, Vol.

10, No. 2, p.90.

•

Biasotti, A. A., "Vise/Rest for Remote Firing," AFTE Journal, Vol. 11, No. 4, p.16.

6.1.11 Downloading

Due to the limitations of a firearms identification section's bullet recovery devices, it may be

necessary to reduce or change the powder load of the cartridge in order to obtain a velocity suitablefor safely collecting test standards for comparison purposes. Even with a reduced load, it may be

necessary to fire the firearm remotely.



o

Test Firing and Recovery of Test Fires

o Primed Cases

• INSTRUMENTATION

o Balance / Scale


Pull the bullet of the cartridge using an inertia bullet puller or a reloading press.

Remove existing powder.

Weigh the pulled bullet.

Consult a reloading manual, such as Lyman, and obtain the powder charge for the weight of the pulled bullet and the new velocity needed.

Weigh out the appropriate powder charge and place in existing cartridge case.

Loosely pack a small piece of tissue or other similar material into the case to fill the gap between the

bullet and powder.

Seat the bullet back into the cartridge case using a rubber mallet or a reloading press.




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If appropriate powder is not available, a reduced load using 50% of the original powder can be used.

It should be noted that great care must be taken when performing this type of downloading. 50%downloading CANNOT be used with slow burning powders. 50% downloading CANNOT be used

with many non-canister powders.

When utilizing downloaded ammunition it is imperative that the examiner checks the barrel for

obstructions between each firing. The bullet, cartridge case, or shotshell of each test shot should bemarked appropriately.

6.1.11.2 REFERENCES

• Lyman Reloading Handbook for Rifle, Pistol and Muzzle Loading, Lyman Gun SightProducts, Middlefield, Conn., 1971.

• "Reduced Powder Loads," AFTE Newsletter, No. 3, p.14.

6.1.12 Primed Cartridge Case/Shotshell

During the course of examining a firearm, it may be determined that it would be unsafe for the

examiner to fire the firearm as designed. If it is not necessary to obtain test standards forcomparison purposes, the firing condition of the firearm can be tested using a primed emptycartridge case or shotshell.



o Bullet Trap


Obtain a primed empty cartridge case in the desired caliber or pull the bullet of a live cartridge using

an inertia bullet puller or reloading press, retaining only the primed cartridge case. For shotguns,obtain a primed empty shotshell in the desired gauge or cut open a live shotshell removing all

components, retaining only the primed shotshell.

• Commercial firing pin testing devices are available for shotguns and may be used.

Proper hearing and eye protection must be worn.

Ensure that the Exhaust fans or system is turned on.

Ensure all warning systems are activated.

Load the primed empty cartridge case, primed empty shotshell or commercial firing pin testing

device into the chamber of the firearm and test fire in front of the bullet trap.

When utilizing a primed empty it is imperative that the examiner check the barrel for obstructions

between each firing.

Repeat if the firearm has more than one action.

Obtain all tests.




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6.1.13 Caliber Determination

Caliber, or the base diameter, is one of the class characteristics of a fired bullet. The determination

of caliber will aid the examiner during the identification or elimination of a suspect firearm. If no

firearm is submitted, the bullet's caliber may be used in determining the General RiflingCharacteristics of the firearm involved.


o Trace Material Examination

o GRC Utilization

• INSTRUMENTATION

o Comparison Microscope

o Stereo Microscope

o Calipers/Micrometer

o

Measuring Projector


The following may be utilized to determine the caliber of any fired bullet. The condition of the bullet will determine which steps can be used.

• Compare the base diameter of the evidence bullet directly with known fired test standards.

• Measure the base diameter of the evidence bullet using a measuring device and compare thismeasurement with known measurements published in reference literature.

• Determine the number and widths of the lands and grooves and compare to Appendix G,Table 6, of the AFTE Glossary (current edition is available on the AFTE website).

• Physical characteristics of the evidence bullet, such as weight, bullet shape, composition,nose configuration, and number and placement of cannelures, may aid in caliber

determination.


Caliber is written as a numerical term and will be depicted with the decimal point when applicable.

If the base is mutilated, the examiner may only be able to determine that the evidence is consistentwith a range of calibers or that the caliber cannot be determined.

6.1.13.3 REFERENCES

•

Mathews, J. Howard, Firearms Identification Vol. I, 1973.

• Barnes, Frank C., Cartridges of the World, 7th Edition, 1993.

• Association of Firearm and Toolmark Examiners Glossary, 3rd Edition, 1994.

• Lutz, Monty C. and Ward, John G., "Determination of Bullet Caliber From an X-ray," AFTEJournal, Vol. 21, No. 2, p. 168.




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6.1.14 Measuring Land Impression and Groove Impression Widths

One of the class characteristics used in the discipline of firearms identification is the width of the

land impressions and groove impressions. These measurements aid the examiner during the

identification or elimination of a suspect firearm. If no firearm is submitted, these measurementswill be used in determining the General Rifling Characteristics of the firearm involved. The

measuring projector procedure utilizes an MP-6 Measuring Projector or equivalent. The comparisonmicroscopes have specific software for measurements. The air gap procedure utilizes a comparison

microscope and a micrometer.



o GRC Utilization

• INSTRUMENTATION

o Measuring Projection Scope

o

Comparison microscopeo Software for the Comparison Microscope

o Stereo Microscope

o Ruler/Micrometer


In measuring a fired bullet to determine the width of the land impression or the groove impression, itis paramount that the points used for beginning and ending a measurement comply with the

discipline-wide practice. This practice utilizes the anchor points shown below.

• For the Measuring Projection Scope:

o The fired bullet in question is mounted in the measuring projector's bullet holder.

o The land impression of the fired bullet is placed in a horizontal position with one of

the anchor points corresponding with the measuring projector's alignment grid.

o Zero the direct reading scale of the measuring projector.


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o Rotate the micrometer, thereby moving the fired bullet laterally, until the next anchor

point is reached and record the measurement in thousandths of an inch or to theappropriate measurement standard for the local laboratory.

o Repeat this procedure for the groove impression.

o For specific operating instructions on the instrument utilized, consult the operator's

manual.

• For the Comparison Microscope using Software

o The fired bullet in question is mounted in the microscope bullet holder.

o (For the FSC microscope) The land impression of the fired bullet is placed in a

horizontal position with one of the anchor points corresponding with the measuringalignment mark.

o For the FSC using the Palm emulator and a live image, select the left or right stage

position on the PALM emulator, select START and move the fired bullet stage

laterally, until the next anchor point is reached and record the measurement in

thousandths (mils) of an inch from the PALM emulator.

o (For the SPOT software) Take a photograph of the desired image with the land

impression or groove impression visible.

o (SPOT software) Draw a measurement line over the portion of interest.. Record the

measurement in thousands of an inch.

o Repeat this procedure for the groove impression.

o For specific operating instructions on the instrument utilized, consult the operator's

manual.

• For Air Gap

o The fired bullet in question is mounted on one stage of the comparison microscope.

The micrometer is mounted on the other stage.

Both stages must be using the same magnification level (objective setting) and

be in focus.

o Align the image of the measurement gap (opening) of the micrometer with the image

of the appropriate land impression being measured and record the measurement to the

nearest hundredth or thousandth of an inch or appropriate measurement.

o Repeat the above utilizing the groove impression.

• For the Stereo Microscope with a ruler/micrometer

o The fired bullet in question is either held or mounted on a steady surface beneath the

stereo microscope.

o The land impression at the base of the fired bullet is placed perpendicular to the scale

of the ruler.




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o Measure the distance between both anchor points of a land impression and record the

measurement to the nearest hundredth or thousandth of an inch or appropriatemeasurement.

o Repeat the above utilizing the groove impression.

6.1.14.2

INTERPRETATION OF RESULTS: It may be necessary to measure several of each land and groove impression in order to record a

reliable measurement.

6.1.14.3 REFERENCES

• U.S. Department of Justice, Federal Bureau of Investigation, NCIC, CriminalisticsLaboratory Information System (CLIS) Operating Manual, 1978.

• Unitron MP-6 Operating Manual.

• Leica FSC Operating Manual.

•

Leica UFM-4 Operating Manual

• SPOT Operating Manual by Diagnostic Instruments

• Leica Application Suite Software

• Walsh, J. F., "Accuracy, Speed and Conversion in Rifling Measurements," AFTE Journal,Vol. 9, No. 1, p. 50.

• AFTE Newsletter, No. 4, December 1969, p. 28.

6.1.15 National Integrated Ballistic Information Network

The National Integrated Ballistics Information Network (NIBIN) is a computerized system for

acquiring and storing the images of unidentified bullets and cartridge cases as well as known bullets

and cartridge cases. NIBIN images portions of the surface (land engraved areas) of a bullet and the primer/firing pin and ejector areas of fired cartridge cases using state of the art optical and electronic

technology. These images are then stored in databases and sophisticated algorithms are used to

correlate the images against each other using filters such as caliber, rifling specifications, date ofcrime and date of entry. These correlations produce lists of possible matches with the highest score

at the top of the list. A firearms examiner or NIBIN technician can then call up the images tocompare them side by side on a monitor. If a possible association is found during this screening

process then the physical items are compared by a firearms examiner utilizing traditional

comparative microscopy techniques. A new employee with the Firearms and Tool Marks section (orsubsection Operation Shutdown) cannot use the NIBIN technology until they have been properly

trained and received clearance through Forensic Technologies, Inc. and the Bureau of Alcohol,

Tobacco, Firearms and Explosives (ATF). Cautions pertaining to electrical equipment and computer

storage media should be observed by anyone utilizing the NIBIN technology.


o Examination and Physical Classification of Fired Evidence

o Examination and Physical Classification of Fired Cartridge Cases




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o Examination and Physical Classification of Fired Shotshells

o Microscopic Comparison

• PREPARATION

o Cartridge Case – The examiner should consider marking the sides of the cartridge

case to indicate where the extractor and/or ejector markings are for proper alignment.

o Bullet - Mount the bullet in the designated holder with a glue gun as outlined in the

IBIS Training Course student handbook.

• INSTRUMENTATION

o Remote Data Acquisition System (RDAS).

• MINIMUM ANALYTICAL STANDARDS and CONTROLS

o In accordance with ASCLD 1.4.1.6 (E), the NIBIN bullet and cartridge case samplesare to be treated as reference material only. If a test fired bullet/cartridge case is used

for comparison purposes at a later date, it will be documented on the examiner’s

report as being a reference bullet/cartridge case previously test fired in the firearmand retained at the Arkansas State Crime Laboratory.

• Test fired bullet and cartridge case reference samples will be maintained in asecure area accessible by Firearms Section personnel. Archived material will

be stored in a secure area in the ASCL Annex.


• A test fire information card will be filled out to include the ASCL case #, item # andidentifying information (if available) for the test firearm. The test fire information card will

be stored with the test fired bullets and cartridge cases.

•

The examiner should consider marking the bullet and cartridge case of each test shot with

the;

o Full or abbreviated laboratory case number and

o Full or abbreviated item number and/or

o examiner's initials.

• If the examiner does not, or is unable to, mark the test fired bullet/cartridge case with theabove information, then the package containing the test fires and information card will be

sealed and initialed.

•

Cartridge Case – Using the RDAS, open the BRASSCATCHER software and enter thespecimen information as outlined in the RDAS operators’ manual or the IBIS Training

Course student handbook.

• Bullet – Using the RDAS, open the BULLETPROOF software and enter the specimen

information as outlined in the RDAS operator’s manual or the IBIS Training Course student

handbook.

• The examiner must therefore insure that;




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o Any evidence bullet selected for entry into NIBIN must have at least one clear and

distinct land engraved area and must have sufficient individual characteristics to beable to affect a match.

o Any evidence cartridge case selected for entry into NIBIN must have sufficient

individual characteristics within the firing pin impression and/or within the breech

face marks on the primer to affect a match.

o If there are more than one matching evidence bullets and/or cartridges cases suitablefor entry into NIBIN, the examiner should select the best one for entry or, if

necessary, more than one if different individual characteristics reproduce better on

different tests.

o Any information about the identification of evidence bullets/cartridge cases to eachother and the selection of certain specimens for entry into NIBIN must be

documented within the case notes.

• For Firearms requests, a notification of entry into the NIBIN system will be included in theexaminer’s report.

• For Operation Shutdown requests, a NIBIN Evidence Evaluation Form (FA-FORM-05) will

be completed and attached to evidence that has been processed/evaluated for entry into the NIBIN system.

6.1.15.2 REFERENCES

• RDAS OPERATORS MANUAL

• IBIS Training Course Student Handbook

6.1.16 GRC Utilization

The FBI's General Rifling Characteristics File can be utilized when attempting to determine a list of possible firearms that could have fired an evidence bullet when the correct firearm was not

submitted.



o Measuring Land Impression and Groove Impression Widths


The General Rifling Characteristics File can be accessed using the PC software version, or the

current printout of the file.Follow the operating instructions listed specifically within each of the above systems utilizing thecaliber and rifling characteristics of the evidence bullet.


The GRC File is an investigative aid and should not be construed as an all-inclusive list of firearms

available with those particular rifling characteristics.




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6.1.16.3 REFERENCES

• U.S. Department of Justice, Federal Bureau of Investigation, NCIC, CriminalisticsLaboratory Information System (CLIS) Operating Manual, 1978.

• Walsh, J. F., "Accuracy, Speed and Conversion in Rifling Measurements," AFTE Journal,

Vol. 9, No. 1, p. 50.• AFTE Newsletter, No. 4, December 1969, p. 28.

6.1.17 Wadding Determination

By examining wadding, the examiner may be able to determine the gauge size, manufacture, and ifthe wad contains markings suitable for comparison, the firearm that discharged it.




•

INSTRUMENTATION


o Stereo Microscope

o Micrometer

o Caliper

o Measuring Projector


•

Determine gauge size by;o Directly comparing the evidence to known laboratory standards of similar

manufacture or composition by comparing the base of evidence to the bases of the

standards until a similar size is found.

o Gauge size can also be determined by measuring the base diameter of the wad and

comparing these measurements to known measurements.

• Measurements may be obtained by utilizing a;

o Caliper

o The air gap

o

The stereo microscope with ruler/micrometer/caliper

o The measuring projector.

• Manufacturers’ data can be determined by locating information stamped into the wad or bycomparing the wad to known laboratory standards.

• Microscopic examination may reveal striations suitable for identification of the wad back tothe shotgun that fired it.




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• If evidence shotshells are submitted, it may be necessary to disassemble one for thedetermination of gauge size or manufacturer.

• Record all information on the appropriate worksheet.


If the wad is mutilated or soaked with blood or other body fluids, the examiner may not be able tospecifically determine gauge size. The examiner should also recognize that some manufacturers

might duplicate the design of another manufacturer.

6.1.18 Shot Determination

By examining recovered shot pellets, the examiner may be able to determine the actual shot size.

The determined size can then be compared to the shot size loaded in submitted live shotshells or to

the size that the submitted discharged shotshell was marked to have contained.


o

Trace Material Examinationo Measuring Land Impression and Groove Impression Widths

• INSTRUMENTATION


o Stereo Microscope

o Micrometer

o Caliper



The examiner may use one or all of the below techniques to determine shot size.

• Visual/Microscopic Comparison

o Determine the total number of pellets received.

o Determine the composition of the pellets.

o Determine the number of pellets suitable for comparison purposes. Make note if

pellet sizes all appear to be similar in size. If several different sizes are present,

determine each specific size.

o

Compare laboratory standards of known shot sizes side by side with the evidence pellets until a known shot size is determined. A stereo microscope may aid in this

determination. This can be done one size at a time or several sizes at a time;

however, if more than one size is used at a time, care should be taken not to mix upthe shot.

o Record findings on worksheet.

• Comparison by Weight




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o Record the total number of pellets received.

o Determine the composition of the pellets.

o Determine the number of pellets suitable for weighing. Make note if pellet sizes all

appear similar. If several sizes present, determine each specific size.

o

Weigh the pellets in grams or grains.

o Divide weight of pellets by total number weighed.

o Consult known pellet weights in Table 1 of Appendix G of the AFTE Glossary (3rd

Edition) and determine shot size, which corresponds to evidence shot.

o The weight of the evidence pellets can also be directly compared to weight of

standards using the same number of pellets until a similar known weight is obtained.

• Measuring Pellet Size

o Determine the total number of pellets received.

o

Determine the composition of the pellets.o Determine the number of pellets suitable for comparison purposes. Make note if

pellet sizes all appear to be similar in size. If several different sizes are present,

determine each specific size.

o Choose the best specimen and measure diameter using a caliper and record inhundredths or thousandths of an inch or the appropriate measurement.

o Consult known pellet sizes in Table 1 of Appendix G of the AFTE Glossary (3rd

Edition) and determine shot size, which corresponds to evidence shot.

6.1.18.2 REFERENCES

•

Association of Firearm and Toolmark Examiners Glossary, 3rd Edition, 1994.

6.1.19 Physical Examination & Classification of Fired Bullet/Slug Evidence

The initial examination of any fired bullet/slug evidence will include the completion of a worksheet.These worksheets will include the physical description of the fired evidence and will serve as a

source to document the condition of the evidence as received and any tests or comparisons

performed.



o

Measuring Land Impression and Groove Impression Widthso Caliber Determination

• INSTRUMENTATION


o Stereo Microscope

o Micrometer




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o Caliper


o Scale/Balance


A worksheet will be filled out according to the appropriate Appendices. This may include noting the

following:

• If any trace material is present.

• The caliber.

• The bullet/slug weight should be measured in grains.

• The number of lands and grooves on a fired bullet.

• The direction of twist.

•

The measured width of the land impressions.• The measured width of the groove impressions.

• The composition of the bullet/slug.

• The bullet style.

• The possible manufacturer/marketer of the bullet/slug/projectile.

• A description of the base of the bullet.

• The type and position of cannelures.

• Any extraneous markings to include:

o Skid Marks

o Shave Marks

o Flared Base

o Other Marks

• The presence of gunpowder and/or powder imprints adhering to the base.

• The condition of the fired evidence as received.

• The suitability of the fired evidence for comparison purposes.

6.1.19.2

REFERENCES

• Howe, Walter, J., “Laboratory Work Sheets” AFTE NEWSLETTER NUMBER TWO,August 1969, p.13.

• Association of Firearm and Toolmark Examiners Glossary, 3rd Edition, 1994.




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6.1.20 Physical Examination & Classification of Fired Cartridge Cases

The initial examination of any fired cartridge case evidence will include the completion of a

worksheet. These worksheets will include the physical description of the fired cartridge case and

will serve as a source to document the condition of the evidence as received and any tests orcomparisons performed.




o Caliber Determination

• INSTRUMENTATION


o Stereo Microscope

o

Micrometero Caliper


o Scale/Balance


A worksheet will be filled out according to the appropriate Appendices and individual laboratory

policy. This may include noting the following:

• If any trace material present.

•

Caliber

• The possible manufacturer/marketer of the item.

• Ignition System

o Centerfire

o Rimfire

o Other

• Shape of cartridge case.

• Description of cartridge case and primer.

• Description of head stamp

• Description of Firing Pin Impression

• Description of other markings, to include:

o Breech Face Markings

o Extractor




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o Ejector

o Resizing Marks

o Chamber Marks

o Anvil Marks

o

Magazine Marks

o Ejection Port Markings

o Other Marks

6.1.20.2 REFERENCES

•

ar firearms quality manual

Documents