ASTM E3309-21

Standard Guide for Reporting of Forensic Primer Gunshot Residue (pGSR) Analysis by Scanning Electron Microscopy/Energy Dispersive X-Ray Spectrometry (SEM/EDS)

SIGNIFICANCE AND USE
4.1 This guide is designed to be used by forensic service providers when issuing final reports on pGSR analyses by SEM/EDS.  
4.2 This guide is intended to be used in conjunction with Practice E1588, Practice E620, and the SWGGSR Guide.
SCOPE
1.1 This guide describes the contents of a formal, written technical report expressing the results and interpretation of pGSR particle analysis by SEM/EDS by forensic service providers.  
1.2 This guide is intended for use by competent forensic science practitioners with the requisite formal education, discipline-specific training (see Practices E2917), and demonstrated proficiency to perform forensic casework.  
1.3 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Aug-2021
• ICS: 07.140 - Forensic science
• Technical Committee: E30 - Forensic Sciences
• Drafting Committee: E30.01 - Criminalistics

Relations

• Refers: ASTM E2917-24 - Standard Practice for Forensic Science Practitioner Training, Continuing Education, and Professional Development Programs
• Effective Date: 01-Feb-2024
• Refers: ASTM E1732-24 - Standard Terminology Relating to Forensic Science
• Effective Date: 01-Feb-2024
• Refers: ASTM E2917-19 - Standard Practice for Forensic Science Practitioner Training, Continuing Education, and Professional Development Programs
• Effective Date: 15-Feb-2019
• Refers: ASTM E1732-19 - Standard Terminology Relating to Forensic Science
• Effective Date: 15-Jan-2019
• Refers: ASTM E1732-18b - Standard Terminology Relating to Forensic Science
• Effective Date: 01-Nov-2018
• Refers: ASTM E1732-18a - Standard Terminology Relating to Forensic Science
• Effective Date: 01-Jun-2018
• Refers: ASTM E1732-18 - Standard Terminology Relating to Forensic Science
• Effective Date: 15-May-2018
• Refers: ASTM E1732-17 - Standard Terminology Relating to Forensic Science
• Effective Date: 01-Sep-2017
• Refers: ASTM E1588-16a - Standard Practice for Gunshot Residue Analysis by Scanning Electron Microscopy/Energy Dispersive X-Ray Spectrometry
• Effective Date: 01-May-2016
• Refers: ASTM E1588-16 - Standard Guide for Gunshot Residue Analysis by Scanning Electron Microscopy/Energy Dispersive X-Ray Spectrometry
• Effective Date: 01-Mar-2016
• Refers: ASTM E1732-12 - Standard Terminology Relating to Forensic Science
• Effective Date: 15-Jun-2012
• Refers: ASTM E1732-11a - Standard Terminology Relating to Forensic Science
• Effective Date: 01-Oct-2011
• Refers: ASTM E1732-11b - Standard Terminology Relating to Forensic Science
• Effective Date: 01-Oct-2011
• Refers: ASTM E1732-11 - Standard Terminology Relating to Forensic Science
• Effective Date: 01-Jun-2011
• Refers: ASTM E620-11 - Standard Practice for Reporting Opinions of Scientific or Technical Experts
• Effective Date: 01-May-2011

Overview

ASTM E3309-21 is the international standard guide for the reporting of forensic primer gunshot residue (pGSR) analysis using Scanning Electron Microscopy/Energy Dispersive X-Ray Spectrometry (SEM/EDS). Developed by ASTM Committee E30 on Forensic Sciences, this guide provides forensic service providers with comprehensive recommendations for documenting and interpreting the results of pGSR particle analysis. The standard is designed to ensure accuracy, consistency, and reliability in forensic science technical reports involving pGSR evidence.

Key Topics

• Scope and Usage: The guide details the required contents of formal technical reports expressing the results and interpretations from pGSR analyses by SEM/EDS. It is intended for trained forensic practitioners with demonstrated proficiency and discipline-specific education.
• Reporting Structure: Provides guidance on the systematic presentation of data, including the type and quantity of pGSR particles, classification terminology (characteristic, consistent, commonly associated), interpretations, and limitations.
• Quality Assurance: Addresses best practices for issuing amended or supplemental reports when errors are detected or additional analyses are performed. Reports must clearly state original report dates and distribution to all recipients.
• Interpretation Guidelines: Offers example wordings for reporting positive, negative, or inconclusive findings, and stipulates that the number of pGSR particles detected cannot be solely used to determine scenarios such as firearm discharge or secondary transfer.
• Transfer Mechanisms and Limitations: Discusses primary, secondary, and tertiary mechanisms for pGSR transfer, as well as factors influencing retention and detection, such as firearm type, collection methods, environmental conditions, and uncertainty sources.

Applications

• Forensic Laboratories: Enables consistent and transparent reporting of pGSR findings, supporting criminal investigations involving firearm discharge or contact with gunshot residue.
• Law Enforcement: Assists in the interpretation of forensic evidence related to shootings, helping establish or exclude possible firearm discharge and reconstruct events.
• Legal Proceedings: Provides documented, standardized reporting language suitable for courtroom testimony and case files, supporting clear communication of forensic evidence to legal professionals and juries.
• Quality and Compliance: Facilitates harmonization with other forensic standards such as ASTM E1588 (pGSR analysis by SEM/EDS), ASTM E620 (expert opinion reporting), and SWGGSR Guides.
• Training and Accreditation: Serves as a reference for training forensic science personnel and as evidence of compliance with internationally recognized standardization principles.

Related Standards

For a comprehensive approach to forensic primer gunshot residue analysis and reporting, the following standards and guides are referenced or recommended for conjunction with ASTM E3309-21:

• ASTM E1588 - Practice for Gunshot Residue Analysis by SEM/EDS
• ASTM E620 - Practice for Reporting Opinions of Scientific or Technical Experts
• ASTM E2917 - Practice for Forensic Science Practitioner Training, Continuing Education, and Professional Development
• ASTM E1732 - Terminology Relating to Forensic Science
• SWGGSR Guide - Guide for Primer Gunshot Residue Analysis by Scanning Electron Microscopy/Energy Dispersive X-ray Spectrometry

Practical Value

By following ASTM E3309-21, organizations and practitioners in the forensic science community ensure that pGSR analysis reports are scientifically defensible, clear, and consistent. This contributes to the credibility of forensic evidence in criminal justice processes and supports the global harmonization of forensic science practices. The standard provides essential guidance for documenting findings from advanced analytical techniques like SEM/EDS, thereby improving transparency and accountability in forensic reporting.

Keywords: ASTM E3309-21, forensic science, primer gunshot residue, pGSR, SEM/EDS, forensic reporting, technical reports, particle analysis, energy dispersive X-ray spectrometry, gunshot residue analysis, crime laboratory standards.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E3309 − 21 An American National Standard
Standard Guide for
Reporting of Forensic Primer Gunshot Residue (pGSR)
Analysis by Scanning Electron Microscopy/Energy
Dispersive X-Ray Spectrometry (SEM/EDS)
This standard is issued under the fixed designation E3309; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Terminology
1.1 This guide describes the contents of a formal, written
3.1 Definitions:
technical report expressing the results and interpretation of
3.1.1 For definitions of terms that can assist in interpreting
pGSR particle analysis by SEM/EDS by forensic service
this standard, refer to Terminology E1732.
providers.
3.2 Definitions of Terms Specific to This Standard:
1.2 This guide is intended for use by competent forensic
3.2.1 background sample, n—a recovered sample from a
science practitioners with the requisite formal education,
source believed not to have been exposed to pGSR.
discipline-specific training (see Practices E2917), and demon-
3.2.1.1 Discussion—Background samples can be used to
strated proficiency to perform forensic casework.
establish a threshold value.
1.3 This international standard was developed in accor-
3.2.2 candidate particles, n—particle(s) classified by the
dance with internationally recognized principles on standard-
instrument software based on detection of appropriate (as
ization established in the Decision on Principles for the
specified in Practice E1588) constituent elements as potential
Development of International Standards, Guides and Recom-
pGSR.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
3.2.3 confirmed particles, n—particle(s) relocated,
analyzed, and classified by the analyst as pGSR based on
2. Referenced Documents
appropriate (as specified in Practice E1588) constituent ele-
2.1 ASTM Standards:
ments and morphology.
E620 Practice for Reporting Opinions of Scientific or Tech-
3.2.4 threshold, n—a value, based on a background sample
nical Experts
study, below which the number of pGSR particles identified
E1732 Terminology Relating to Forensic Science
cannot be distinguished from background levels and thus
E1588 Practice for Gunshot Residue Analysis by Scanning
cannot be reliably interpreted as associated with the discharge
ElectronMicroscopy/EnergyDispersiveX-RaySpectrom-
of a firearm or contact with a source of pGSR.
etry
E2917 Practice for Forensic Science Practitioner Training,
4. Significance and Use
Continuing Education, and Professional Development
Programs
4.1 This guide is designed to be used by forensic service
2.2 Other Documents: providers when issuing final reports on pGSR analyses by
SWGGSR Guide for Primer Gunshot Residue Analysis by SEM/EDS.
Scanning Electron Microscopy/Energy Dispersive X-ray
4.2 This guide is intended to be used in conjunction with
Spectrometry
Practice E1588, Practice E620, and the SWGGSR Guide.
This guide is under the jurisdiction of ASTM Committee E30 on Forensic
5. Report
Sciences and is the direct responsibility of Subcommittee E30.01 on Criminalistics.
Current edition approved Sept. 1, 2021. Published October 2021. DOI: 10.1520/ 5.1 The report reflects interpretations based on the classifi-
E3309-21.
cation of particle data from the results of instrumental analysis,
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
and on associated definitions in Practice E1588, the SWGGSR
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Guide, and the scientific literature.
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
5.2 Pertinent Information—Satisfy the requirements of
Available from Scientific Working Group for Gunshot Residue, https://
www.swggsr.org. Practice E620, Section 4.7, by listing:
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E3309 − 21
5.2.1 The general examinations conducted, including the 5.4.2.2 No (zero) particles confirmed as either characteristic
generic class and type of instrumentation used and the disci- of or consistent with pGSR were detected on the (sample
pline specific technique, methodology, or procedure per- source).
formed. 5.4.2.3 (Numerical value) particles characteristic of pGSR
5.2.1.1 Example Wording—Exhibit 1 was examined by were confirmed but were below the established threshold level
to be considered distinguishable from background levels based
SEM/EDS for the presence of pGSR particles based on
upon previously conducted background studies.
elemental constituents and morphology.
5.4.2.4 (Sample source) contained only particles that one
5.2.2 Best practice is to report the quantity of the confirmed
might expect to see in typical background samples.
pGSR-related particles.
5.4.3 Example wordings for inconclusive or indeterminate
5.2.3 Report the type of particle found using the terms
results. For inconclusive or indeterminate results, use wording
characteristic, consistent, and commonly associated with
that clearly indicates to the reader that the analytical data
pGSR. Provide definitions of these terms in the report or in an
cannot be interpreted unambiguously. This result could be due
appendix.
to factors such as contamination, unusual particle populations,
5.2.3.1 The elemental constituents for each particle or
or unusual elements present in particles. Further testing could
particle class can also be included in the report.
be warranted (1).
5.2.4 If a threshold value is used, state the value in the
5.4.3.1 The particles on the (sample source) cannot be
report.
unambiguously interpreted as pGSR due to ______.
5.3 Descriptive Information—Meet the requirements of
5.4.3.2 The presence of [atypical element(s)] in combina-
Practice E620, Section 4.7, and:
tion with lead, barium, and antimony is uncommon in charac-
5.3.1 If errors are detected in a report, issue an amended
teristic pGSR. Therefore, these particles cannot be unambigu-
report that contains the reasons for the amendments. Clearly
ously distinguished as either routine background or pGSR.
indicate that it is an amended report and include the date of the
Submission of additional reference materials (spent cartridge
original report.
case, weapon, clothing, etc.) for additional testing could result
5.3.2 If additional work is performed after the original
in a more conclusive interpretation.
report is issued, issue a supplemental report. Clearly indicate
5.4.3.3 Characteristic pGSR particles were detected on the
on the supplemental report that it is supplemental and include
negative control. This suggests that any pGSR particles found
the date of the original report.
on the sample could have resulted from contamination and
5.3.3 Distribute amended and supplemental reports to all
therefore no unambiguous interpretation can be made.
recipients of the original report.
5.5 Interpretations and Limitations—Meet the requirements
5.4 Results—Meet the requirements of Practice E620, Sec-
of Practice E620, Section 4.8 and 4.9. The examples listed
tions 4.8 and 4.9. The example wordings provided below do
below do not purport to show all possible reporting styles and
not purport to show all possible reporting styles and can be
can be subject to style modifications.
subject to style modifications.
5.5.1 Interpretations can be drawn from the identification of
5.4.1 Example wordings based on confirmed particles de- characteristic pGSR particles on a recovered sample from a
tected on the recovered sample, either consistent with, or person. Include wording stating that the identification of
characteristic of pGSR. characteristic pGSR particles is consistent with the following
interpretations: (1) the person discharged a firearm; (2) the
5.4.1.1 (Numerical Value) particles characteristic of pGSR
person was in the vicinity of a firearm discharge; or (3) the
and (numerical value) particles consistent with pGSR were
person came in contact with something that had pGSR on it.
confirmed on the (sample source).
Thenumberofconfirmedparticlescannotbeusedtodetermine
5.4.1.2 (NumericalValue) particles containing lead, barium,
which of these scenarios is more likely.
and antimony (characteristic) were confirmed on the (sample
5.5.1.1 Example Wording—The subject could have dis-
source).
charged a firearm, handled a discharged firearm, been in the
5.4.1.3 At least (threshold value) particles characteristic of
vicinity of a discharged firearm, or contacted an object with
pGSR were confirmed on the (sample source).
pGSR on it.
5.4.1.4 (Numerical value) particles containing (elemental
5.5.2 Interpretations can be drawn from the identification of
constituents) were confirmed on the (sample source).
pGSR particles on a recovered sample from an inanimate
5.4.2 Example wordings based on the absence of confirmed
object. Include wording stating that the identification of char-
particles detected on the recovered sample, either consistent
acteristic pGSR particles on an inanimate object is consistent
with, or characteristic of pGSR.
with, at some time in its history, (1) having contacted a
5.4.2.1 No (zero) characteristic pGSR particles were de-
pGSR-related item, (2) having been in the vicinity of a firearm
tected on the (sample source).
discharge; or (3) having had pGSR transferred to it from a
person or another object.
For use by laboratories with an established threshold value. Laboratories must
be able to provide the supporting background sample study and data interpretation
which the threshold value is based on, if requested. An Appendix to the report can The boldface numbers in parentheses refer to a list of references at the end of
be used to detail the specific number and classification of particles detected. this standard.
E3309 − 21
5.5.2.1 Example Wording—(Sample source) contacted a control reference sample. Clearly state that these particles
pGSR-related item, was in the vicinity of a firearm discharge, could also be from a non-firearm source.
or had pGSR transferred to it.
5.5.7 When comparing results to a known ammunition,
include the details of the elements and combinations of
5.5.3 Interpretations can be drawn from the identification of
elements that are being considered in the interpretation. Indi-
consistent pGSR particles on a recovered sample from a
cate these particle types could originate from other
person. Include wording stating that the identification of
ammunitions, unless the ammunition in this case is manufac-
consistent pGSR particles is consistent with the following
tured for a unique application, such as ammunition with
interpretations: (1) the person discharged a firearm; (2) the
taggant elements.
personwasinthevicinityofafirearmdischarge;(3)theperson
5.5.8 Attach an explanatory statement or page to help the
came in contact with something that had pGSR on it; or (4) the
reader understand any distinctive circumstances associated
person came into contact with a non-firearm source of these
withtheinvestigation.Examplesofexplanatorystatementsare:
particles. The number of confirmed particles cannot be used to
5.5.8.1 Consistent particles are known to be associated with
determine which of these scenarios is more likely.
pGSR. More information regarding their possible origin could
5.5.3.1 Example Wording—Consistent pGSR found on
be provided if the known firearm or ammunition is submitted
samples recovered from the subject can come from: non-
for further testing.
firearm sources, a firearm discharge, handling a firearm, being
5.5.8.2 Particles of pGSR can be present on victims of a
in the vicinity of a firearm discharge, or coming into contact
gunshot-related injury.
with an object that has consistent pGSR on it.
5.5.8.3 Published studies have shown that residue from
5.5.4 Interpretations can be drawn from recovered samples
certain fireworks, brake pads, or airbag detonators can contain
inwhichpGSRparticlesareabsent.Includewordingthatstates
pGSR-like particles; however, there are typically elemental
that the results suggest, but do not prove, that either there was
indicators that exclude these particles from being identified as
no association with the discharge of a firearm, or that the
pGSR (2-6).
sample source could have been exposed to pGSR, but the
5.5.8.4 Law enforcement officers, active duty military
pGSR particles were not present when the recovered samples
personnel, hunters, or firearm enthusiasts can be a source of
were collected. Do not confuse the absence of pGSR particles
pGSR.
with inconclusive interpretations. The absence of pGSR par-
5.5.8.5 Transfers of pGSR particles from secondary and
ticles supports the theory that an item was not exposed to
tertiary sources are possible. However, there is currently
pGSR.
insufficient data in the literature to estimate the frequency of
5.5.4.1 Example Wording—There is no indication that the
these occurrences.
(sample source) has any association with the discharge of a
5.5.8.6 In general, the elemental constituents and morphol-
firearm. However, the absence of pGSR particles does not
ogy are not sufficiently distinctive to allow using pGSR
prove that a person did not discharge a firearm. It is possible
evidencetoidentifyaspecificfirearmorammunition;however,
that the (sample source) did discharge a firearm, but that pGSR
there are exceptions, such as ammunition containing taggants
particleswerenotdeposited,wereremovedbyactivity,orwere
(see SWGGSR).
not detected.
5.6 Remarks/Additional Information—Include remarks or
5.5.4.2 Example Wording—There is no indication that the
additional information in the report. Specific references for a
(sample source) came into contact with pGSR or was in the
topic are listed in the References and Related Material sections
vicinity of a firearm during discharge. If (sample source) was,
at the end of this guide.
then the pGSR was not deposited, not detected, or removed.
5.6.1 ThereisnoestablishederrorrateforpGSRanalysisby
5.5.5 No interpretations can be drawn from an analysis with
SEM/EDS.
inconclusive results.
5.6.2 Limitations and sources contributing to uncertainty of
5.5.5.1 Example Wording—No determination can be made
measurementinpGSR.Statement(s)relatedtofactorsaffecting
from the (sample source) for the following reason(s) _____.
uncertainty in the number of pGSR particles identified on the
Submission of additional evidence could yield conclusive
sample and limitations can be listed in the report. Some of
findings.
these factors are:
5.5.6 No interpretations can be drawn from the identifica-
5.6.2.1 Primary Transfer Considerations—Factors that can
tionofparticlesthatarecommonlyassociatedwithpGSR.This
influence the number of particles identified:
includes lead, barium, or antimony particles found in isolation
(1) Formation factors including, but not limited to, effects
in the absence of characteristic and consistent pGSR particles.
based on type of firearm, physical condition of firearm, caliber
Do not report the confirmation of such particles as potentially
of firearm, and type of ammunition (7-13).
having originated from the discharge of a firearm, except
(2) Deposition factors including, but not limited to, effects
possibly in the case of the following:
based on number of rounds fired, proximity to discharging
5.5.6.1 Interpretations can be drawn from the identification firearm, physical barrier preventing deposition of PGSR (for
of particles commonly associated with pGSR when high levels example, gloves, hands in pockets, etc.), and environmental
of small spherical lead particles that are known to be found in conditions (for example, wind, rain, etc.
...