Scientific & Technical Review

Panel Final Report for

OSAC 2022-S-0017 Standard

Guide for

Microspectrophotometry in

Forensic Fiber Analysis

Organization of Scientific Area Committees (OSAC) for Forensic Science
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STRP Final Report

OSAC 2022-S-0017 Standard Guide

for Microspectrophotometry

in Forensic Fiber Analysis

Organization of Scientific Area Committees (OSAC) for Forensics Science

September 06, 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

• Cary Oien (Chair), FBI Laboratory

• John Burdett, Craic Technologies

• Elaine Pagliaro, University of New Haven

• Emily Runt, Boston Police Crime Laboratory

• Kristy Sekedat, Michigan State Police

• Mike Smith, FBI Laboratory

• Scott Stoeffler, The McCrone Group

Report Summary:

The Scientific and Technical Review Panel (STRP) for “Standard Guide for

Microspectrophotometry in Forensic Fiber Analysis” 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 Candie Shegogue, Trace Materials Subcommittee

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

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The STRP began its review process with a kickoff meeting on April 7, 2022, and concluded with

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

Trace Materials Subcommittee | NIST.

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 believes the “Standard Guide for

Microspectrophotometry in Forensic Fiber Analysis” (draft standard) clearly

documents that color is an inherent and highly discriminating property of fibers and

that colorimetric measurements are a valid and useful component of a forensic fiber

examination. The instrument and methodology described allows measurements of

absorption in the visible wavelength range to be made on fiber samples in an

objective and reproducible way, including suitable guidance on selection of

instrumental parameters, and adequate descriptions of protocols for verifying proper

and consistent instrument function. The draft standard suitably places the described

methodology within the overall context of a forensic fiber examination, outlining both

techniques which provide information about fiber composition and other techniques

which can be used for comparing and measuring color/dye content of fibers. The draft

standard also provides guidance on the use of spectral measurements acquired using

microspectrophotometry in comparing fiber samples and reporting conclusions,

including limitations of the technique.

1.2 Minority View - None

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 STRP believes that this draft standard adequately addresses

issues related to human factors and performance. The standard explicitly recognizes the

relevance of human factors such as experience, training, and proficiency, and the

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need to conduct consistent or similar analytical parameters to evaluate data and to

compare spectra. The methods described provide objective measurement of the color

of samples. In addition, the standard makes it clear that this is only one part of a

multi-analytical approach used in the analysis of fibers and cannot be relied upon as

the sole means of determining possible source attribution.

2.2. Consensus View - The STRP also believes that human factors are further considered

in additional documents such as OSAC 2022-S-0029 Standard Guide for

Interpretation and Reporting in Forensic Comparisons of Trace Materials, which

must be used to guide the examiner in reaching appropriate conclusions after

conducting this analysis and reporting findings.

2.3. 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 this draft standard adequately addresses quality

assurance. Instrument performance, interpretation of data, and required

documentation are discussed in various sections. The draft references standards

including ASTM E3255 and E620, which discuss quality assurance and report

writing, respectively. ISO 17025 is also referenced in the draft. We have become

aware that a quality assurance document for the trace evidence discipline will be

published in the future, which will be more robust in the quality assurance guidelines

for trace evidence Forensic Science Practitioners.

3.2. Minority View - None

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 views the language set forth in the scope and purpose to

be well defined for use as a standard guide for a competent forensic science
practitioner, clearly delineating that this document/technique is intended to be used as

one part of a larger pool of techniques. With this audience in mind, the proposed

language and terminology of the document is appropriate for the specified purpose

and scope.

4.2. Minority View - None

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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 finds that the draft standard defines appropriate terms

with specialized meaning within the application of microspectrophotometry to fiber

evidence. The STRP notes that while the terminology and definitions are appropriate for

the intended audience of this draft standard (i.e., forensic science practitioners), the

terminology and definitions may not be inherently familiar to a non-expert.

5.2. Consensus View - The STRP believes that this Standard Guide would benefit from

the addition of the definition of “exclusionary difference” in the Terminology Section

(Section 3). The following OSAC Preferred Term for Exclusionary Difference

(08/02/2022) should be used: “A difference in one or more characteristics between

compared items that is sufficient to determine that the compared items did not

originate from the same source, are not the same substance, or do not share the same

composition or classification. NOTE: What is sufficient depends on the performance

and limitations of the method used on the material in question.”

5.3. 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 considers the draft standard to meet the method

description requirement. This is based on the observation that the standard provides a

cogent description of the rationale for performing the testing (sections 4.3 and 5.1-

5.2). It provides a clear rationale for the standard (section 5.3) and describes

conditions that may impact the results or limit their value (section 5.4). The draft
standard provides a useful description of the required sample preparation and

handling (section 6), and a detailed description of the performance checks required

(section 7). Section 8 of the document provides essential information on the

components of the optics and detection systems comprising the instrument and their

optimization. Section 9 provides substantial guidance on conducting the

measurements. Section 10 provides useful guidance for interpreting the results of the

measurements. The STRP verified that the standard minimizes ambiguity while

leaving the document sufficiently flexible to be of value for use with a wide range of

microspectrophotometric instrumentation. The overall level of detail is also sufficient

to make it useful and instructive to practitioners.

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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 - The STRP has found the measurement methods detailed in this

guide to be sufficiently well described and scientifically sound but notes that the

interpretation and reporting guidelines provided are quite broad (e.g., 11.1 details

necessary to support the interpretations). In combination with ASTM E620 Practice for

Reporting Opinions of Scientific or Technical Experts, the guidance provided in Section

10 for comparison and interpretation of data is well laid out for a competent forensic

science practitioner in what details can support their interpretations, but the standard

does not adequately define “exclusionary differences”. If the OSAC

Preferred Term of “Exclusionary Differences” is added to Section 3 Terminology, the

interpretation and reporting will also then be scientifically sound and sufficiently well

described.

• 8/2/2022 OSAC Preferred Term for Exclusionary Difference: A difference in one or

more characteristics between compared items that is sufficient to determine that the

compared items did not originate from the same source, are not the same substance,

or do not share the same composition or classification. NOTE: What is sufficient

depends on the performance and limitations of the method used on the material in

question.

7.2. Minority View - None
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