Scientific & Technical Review

Panel Final Report for

2022-S-0002

Standard Practice for the

Identification of Compounds

Related to Organic Gunshot

Residue (OGSR) by Gas

Chromatography– Mass

Spectrometry (GC-MS)

Organization of Scientific Area Committees (OSAC) for Forensic Science

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STRP Final Report

2022-S-0002

Standard Practice for the Identification of

Compounds Related to Organic Gunshot

Residue (OGSR) by Gas

Chromatography– Mass Spectrometry

(GC-MS)

Organization of Scientific Area Committees (OSAC) for Forensics Science

July 21, 2022]

Disclaimer:

This report was produced by an independent Scientific and Technical Review Panel (STRP). The

views expressed in the report do not necessarily reflect the views or policies of the U.S.

Government. Visit the OSAC website for more information on OSAC’s STRP process.

Scientific & Technical Review Panel Members

• Suzanne Bell, West Virginia University (Retired)

• Cedric Neumann, Battelle

• Claude Roux, University of Technology Sydney

• Tiffany Roy, Forensic Aid, LLC

• Rodney Simmons, Wyoming Division of Criminal Investigation

• Pate Skene, University of Colorado Boulder

• Tatiana Trejos, West Virginia University
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Report Summary:

The Scientific and Technical Review Panel (STRP) for “Standard Practice for the Identification

of Compounds Related to Organic Gunshot Residue (OGSR) by Gas Chromatography– Mass

Spectrometry (GC-MS)” is an independent panel appointed by the National Institute of Standards

and Technology (NIST). A STRP is established with a range of experts to consider how well a

standard meets the needs of the forensic science, law enforcement, and legal communities, and to

recommend improvements to the standards under review. The STRP appreciates the efforts of

Candice Bridge, Ignitable Liquids, Explosives, & Gunshot Residue Subcommittee affiliate, while

serving as the subcommittee liaison to this STRP during the review process.

The STRP began its review process with a kickoff meeting on November 8, 2021, and concluded

with this STRP final report. The panel reviewed the draft standard and prepared comments for

the Ignitable Liquids, Explosives, & Gunshot Residue Subcommittee.

Report Components:

The STRP reviewed this draft standard against OSAC’s STRP Instructions for Review which

include the following content areas: scientific and technical merit, human factors, quality

assurance, scope and purpose, terminology, method description and reporting results. The details

below contain a brief description of each reviewed content area and the STRP’s assessment of

how that content was addressed in the Draft OSAC Proposed Standard.

1. Scientific and Technical Merit: OSAC-approved standards must have strong scientific

foundations so that the methods practitioners employ are scientifically valid, and the

resulting claims are trustworthy. In addition, standards for methods or interpretation of

results must include the expression and communication of the uncertainties in measurements

or other results.

1.1 Consensus View – The STRP finds this draft standard to be scientifically and

technically sound to establish minimum requirements for the qualitative identification

of organic compounds typically associated with the discharge of a firearm (organic

Gunshot Residue or OGSR) using gas chromatography-mass spectrometry (GC-MS).

The draft standard describes the analytical criteria for a GC-MS assay including
typical target compounds and quality assurance and quality control procedures.

Example instrumental operating procedures are included which will be useful to

forensic science service providers (FSSPs). A detailed table in the standard describes

typical target analytes and includes target ions and references. The draft standard is

limited to the analytical methodology and compound identification. It does not

describe or address interpretation of the analytical results for an analyst to render a

conclusion or opinion with respect to the presence or absence of OGSR.

1.2 Minority View – None

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2. Human Factors: All forensic science methods rely on human performance in acquiring,

examining, reporting, and testifying to the results. In the examination phase, some standards

rely heavily on human judgment, whereas others rely more on properly maintained and

calibrated instruments and statistical analysis of data.

2.1. Consensus View –The standard, as revised, provides significant and valuable

procedures for reducing potential biases. Much of this work is done by

articulating clear criteria for examiners to consider when evaluating,

documenting, and interpreting results. By specifying appropriate criteria for

these critical steps, the standard appropriately mitigates subjective judgments

to reduce the potential for cognitive biases that may influence conclusions.

While most sections of the standard provide criteria for evaluation and

interpretation that are sufficiently specific to reduce cognitive biases and other

human factors concerns, there are some exceptions. One remaining concern is

Section 8.3.2.5 (background subtraction). A previous comment flagged this

section but did not offer specific guidance on a proposed revision. The STRP

suggests revisions to this section that: (1) specify the conditions or specific

criteria for examiners to address when deciding whether background spectral

subtraction is appropriate; and (2) either specify a validated procedure or

provide normative references on validated methods for selecting appropriate

background control samples and performing spectral subtraction.

The directive in sections 8.3.2.3 and 8.3.2.4 are vague (e.g., “generally agree”,

“majority”, “similar”). If it is not feasible to assign specific values (such as the

5% criteria for low abundance ions), explanations are vital. Analysts must

clearly explain in their notes why they are or are not considering differences

(e.g., missing or extra peaks or % relative abundance differences) between the

certified reference material (CRM) and known spectra as part of compound

identification.

Criteria for Selected Ion Monitoring (SIM) analysis (such as # ions) should be

spelled out if the scope of the analysis is to include SIM methodology
2.2. Minority View – None

3. Quality Assurance: Quality assurance covers a broad range of topics. For example, a

method must include quality assurance procedures to ensure that sufficiently similar results

will be obtained when the methodology is properly followed by different users in different

facilities.

3.1. Consensus View – The STRP believes that quality assurance and quality control

procedures are properly addressed in Section 9 of this standard.

3.2. Minority View – None

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4. Scope and Purpose: Standards should have a short statement of their scope and purpose.

They should list the topics that they address and the related topics that they do not address.

Requirements, recommendations, or statements of what is permitted or prohibited do not

belong in this section.

4.1. Consensus View – The STRP believes that the scope and purpose of the

standard is clearly stated.

4.2. Minority View – None

5. Terminology: Standards should define terms that have specialized meanings. Only rarely

should they give a highly restricted or specialized meaning to a term in common use among

the general public.

5.1. Consensus View – The STRP believes that all relevant terminology is clearly

defined in the draft standard.

5.2. Minority View – None

6. Method Description: There is no rule as to the necessary level of detail in the description of

the method. Some parts of the method may be performed in alternative ways without

affecting the quality and consistency of the results. Standards should focus on standardizing

steps that must be performed consistently across organizations to ensure equivalent results.

Alternatively, standards can define specific performance criteria that are required to be

demonstrated and met rather than specifying the exact way a task must be done. For example,

it may be enough to specify the lower limit for detecting a substance without specifying the

equipment or method for achieving this limit of detection.

6.1. Consensus View – The STRP believes that the draft standard provides sufficient

information in the method description. Concerns regarding compound

identification procedures are described in Human Factors.
6.2. Minority View – None

7. Reporting Results: Methods must not only be well described, scientifically sound, and

comprehensive but also lead to reported results that are within the scope of the standard,

appropriately caveated, and not overreaching.

7.1. Consensus View – This topic was not applicable to this draft standard. It does

have a “Records” section that describes what data and information is to be

recorded and stored. The STRP believes this section is adequate given the scope

of the draft standard.

7.2. Minority View – None

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