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OSAC RESEARCH NEEDS ASSESSMENT FORM

Title of research need: Quantitative Metrics for GSR Analysis

Keyword(s): Gunshot Residue, GSR, Quantitative Metrics, K-ratios

Submitting subcommittee(s): Ignitable Liquids, Explosives, & 

Gunshot Residue 

Date Approved: 3/02/2021

(If SAC review identifies additional subcommittees, add them to the box above.)

Background Information:

1. Does this research need address a gap(s) in a current or planned standard? (ex.: Field identification system 

for on scene opioid detection and confirmation)

Yes, this research need addresses the establishment of a quantitative metric by which GSR data can be evaluated 

to determine the class in which each particle is placed. The current standard for gunshot residue classification of 

particles depends upon the manual review of energy dispersive X-ray spectra to determine the list of elements 

present. Relying on the experience and judgement of an analyst is subjective. Not all analysts will identify the 

same elements present and may therefore possibly assign the particles to a different particle class. Classification 

can be made objective by interpreting the spectra relative to the spectra from pure elements. A long-established 

mechanism to evaluate spectra objectively is by using the k-ratio, the ratio of intensity in the unknown spectrum 

relative to the intensity in a pure element spectrum. The k-ratio can be used to develop quantitative rules to 

assign particles to classes based on the quantitative measures of their elemental constituents. k-ratios are an 

objective metric which could eliminate much of the subjectivity in assigning particles to classes. There is 

currently insufficient data in the literature to construct quantitative rules for mapping k-ratio data into gunshot 

residue relevant particle class assignments. The research would involve collecting large quantities of gunshot 

residue data, quantifying it using k-ratios and developing quantitative rules to assign particles to descriptive 

classes including the currently used classes (characteristic, consistent with and associated with). Subsequent 

research could be useful for identifying particles from lead-free and other challenging primer types, as well as, 

developing rules for materials like fireworks with similar k-ratio signatures. The accuracy of the method created 

to determine the quantitative metric, and this will need to be demonstrated. The quantitative metric will need to 

be usable by existing automated GSR software users and platforms or be able to be incorporated in the existing 

software.

2. Are you aware of any ongoing research that may address this research need that has not yet been published 

(e.g., research presented in conference proceedings, studies that you or a colleague have participated in but 

have yet to be published)?

Yes, small scale studies have been performed but have not yet been published due to more data needed for a full 

quantitative metric to be determined.
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3. Key bibliographic references relating to this research need: (ex.: Toll, L., Standifer, K. M., Massotte, D., eds. 

(2019). Current Topics in Opioid Research. Lausanne: Frontiers Media SA. doi: 10.3389/978-2-88963-180-3)

[1] N. Ritchie. Quantitative Metrics for IGSR Particle Elemental Identification. In preparation.

[2] ASTM International. ASTM E1588-20: Standard Practice for Gunshot Residue Analysis by Scanning 

Electron Microscopy/Energy Dispersive Xray Spectrometry. ASTM International West Conshohocken, PA, 

USA, 2020.

[3] A. Schwoeble, and D. Exline. Current Methods in Forensic Gunshot Residue Analysis. CRC Press, 2000.

[4] SWGGSR. Guide for Primer Gunshot Residue Analysis by Scanning Electron Microscopy/Energy 

Dispersive X-ray Spectrometry. SWGGSR, 2011. https://www.swggsr.org/publications

[5] J. Goldstein, D. Newbury, D. Joy, C. Lyman, P. Echlin, E. Lifshin, L. Sawyer, and J. Michael. Scanning 

Electron Microscopy and X-Ray Microanalysis. Kluwer Academic/Plenum Publishers, New York, 3 Edition, 

2003.

[6] J. Armstrong. Monte Carlo and zaf/phi (rho z)-based Approaches for Quantitative Analysis on Individual 

Particles: Evaluation of Effect of Size, Shape, and Density Uncertainty on Analytical Results. Scanning. 2006, 

28, 116.

[7] J. T. Armstrong. Methods of Quantitative Analysis of Individual Microparticles with Electron Beam 

Instruments. Scanning Electron Microscopy. 1978, 455.

[8] C. Powell, and A. Jablonski. The NIST Electron Effective Attenuation-Length Database. Journal of Surface 

Analysis. 2002, 9, 322.

[9] ISO/IEC GUIDE 98-3:2008. Uncertainty of measurement — Part 3: Guide to the expression of 

uncertainty in measurement (GUM:1995).

[10] F. Schamber. A Modification of the Linear Least-Squares Fitting Method which Provides Continuum 

Suppression. Ann Arbor Science Publishers. 1977, 241.

[11] L. Currie. Nomenclature in Evaluation of Analytical Methods Including Detection and Quantification 

Capabilities. Analytica Chimica Acta. 1999, 391, 105.

[12] JCGM 102:2011 (Joint Committee for Guides in Metrology). Evaluation of Measurement Data–

Supplement 2 to the “Guide to the Expression of Uncertainty in Measurement” - Extension to Any Number 

of Output Quantities. 2011. http://www.bipm.org/utils/common/documents/jcgm/JCGM_102_2011_E.pdf

[13] N. Ritchie. Using DTSA-II to Simulate and Interpret Energy Dispersive Spectra from Particles. Microscopy 

and Microanalysis. 2010, 16, 248.

4. Review the annual operational/research needs published by the National Institute of Justice (NIJ) at 

https://nij.ojp.gov/topics/articles/forensic-science-research-and-development-technology-working-groupoperational#latest? Is your research need identified by NIJ?

No.
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5. In what ways would the research results improve current laboratory capabilities?

The research result will improve the procedure by which a GSR analyst categorizes a particle based on the 

quantitative metric.

6. In what ways would the research results improve understanding of the scientific basis for the 

subcommittee(s)?

The research result will improve the understanding of the quantitative analysis of the data produced from a GSR 

test result. The established quantitative metric could be incorporated into a future revision of ASTM 1588.

7. In what ways would the research results improve services to the criminal justice system?

The research results would allow for a more precise and reproducible interpretation of gunshot residue test 

results in reports and in courts of law. 

8. Status assessment (I, II, III, or IV): II

Major gap in 

current 

knowledge

Minor gap in 

current 

knowledge

No or limited

current research is 

being conducted I III

Existing current 

research is being 

conducted II IV

This research need has been identified by one or more subcommittees of OSAC and is being provided as an 

informational resource to the community.