LRC Comments to ASTM E3085-17

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COMMENTS BY THE OSAC LEGAL RESOURCE COMMITTEE (LRC)

TO: Materials (Trace) Subcommittee of the Chemistry-Instrumental SAC

FROM: Lynn Garcia, LRC Liaison to Chemistry-Instrumental Analysis SAC

RE: OSAC LEGAL RESOURCE COMMITTEE (LRC) COMMENTS ONE3085-17

Introduction

The Chemistry SAC has proposed the addition of the recently revised “Standard Guide for Fourier 

Transform Infrared Spectroscopy in Forensic Tape Examinations” (ASTM E3085-17) to the OSAC 

Registry of Approved Standards. On the basis of the information that has been provided to us, we 

believe that, with certain modifications, the standard can be included in the Registry of Approved 

Standards. Absent these modifications however, the LRC does not believe the standard guide is ready 

for the Registry. 

Guidelines on Ascertaining “Meaningful Differences” Are Missing

The standard defines a “meaningful difference” as “a feature or property of a sample that does not fall 

within the variation exhibited by the comparison sample, considering the limitations of the sample or 

technique, and therefore indicates the two samples do not share a common origin.” § 3.1.6. The 

standard adds that “[t]he use of this term does not imply the formal application of statistics.” § 3.1.6.1. 

Our major concern is that the remainder of the standard offers no guidance on how to ascertain 

whether a difference is meaningful.

1The standard states "Spectra cannot be distinguished if they 

contain no meaningful differences," and then some examples are given.

The list of variables to consider (§ 8.5.1) is helpful, for it directs the analyst’s attention to the 

properties of the spectra that should be compared. But it is not clear what “variation exhibited by the 

comparison sample” (§ 3.1.6) means for these properties. Is there any variation exhibited by the 

comparison sample in “the presence or absence of absorption bands, their positions, shapes, and 

relative intensities”? Isn’t a band either present or absent? Whichever it is, there is no variation. 

Likewise, the position is where it is. The shape and relative intensity are what they are. The 

subsections do not describe the kinds of variations in presence, positions, shapes and intensities (either 

in the comparison sample itself or between the two samples being compared) that should be deemed 

“meaningful.”

 

1We also note that the phrasing of § 3.1.6.1 is awkward—the use of the term “meaningful difference” does not imply the 

informal application of explicit statistics either, although it necessarily rests on statistical reasoning about variability. We 

suspect the sentence should be rephrased as follows: “Meaningful differences can be discerned without a quantitative 

analysis.” This observation is an editorial comment. If the sentence on statistical reasoning were the only item to be revised, 

it would not prevent approval of the standard.
LRC Comments to ASTM E3085-17

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It may be that the standard isintended to make these determinations entirely subjective and not 

governed by any explicit standards.If that is the recommendation or assumption, the document should 

say so, and it should identify the particular references that estimate the accuracy and reliability of these 

subjective judgments of “meaningful differences.” 

Documentation

We applaud the inclusion of Section 9, on documentation, in the standard. Consideration should be 

given to including a further section on reporting and testifying. If these matters are to be addressed in a 

separate standard—such as the Standard Practice for Interpretation and Report Writing in Forensic 

Comparison of Trace Materials—that fact should be mentioned.

Section 9.1 states that “[w]hen making comparisons of tape samples, the analyst’s assessment of the IR 

spectra shall be documented.” To provide guidance on what is required or recommended, this section 

should describe the type of information that should be in this documentation. For example, the analyst 

might be asked to annotate two spectra to show the differences that were considered.

Section 9.3 states that “[c]ase notes shall include a copy of the instrumental data that was used to reach 

a conclusion. All paper and electronic copies that are retained as part of the case file shall include a 

unique sample designation, the operator’s name or initials, and the date of analysis.” The word 

“includes” connotes that this list does not exhaust the necessary contents of the case notes, and one can 

infer from Section 9.1 that the documentation of the assessment of the spectra must be in the case 

notes, but this should be made explicit by stating that the case notes should also include the 

documentation of the assessment made by analyst on the spectra as well as all information necessary 

for an independent examiner to conduct a later analysis of the original analysis and the conclusions 

reached.

Section 9.4 states that “[a] description of the evidence analyzed by IR, the method of sample 

preparation, the analytical instrumentation used, mode of operation (transmission, ATR, etc.), and its 

operating parameters shall be included in the case notes or in the procedural manuals.” The case notes 

themselves should contain the operating parameters. At a minimum, they must include a notation that 

is information is available in the instrument manuals.

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DISCLAIMER:The failure of any member of the Legal Resource committee (LRC) to provide a 

comment, identify a legal issue or join in another LRC comment should not be interpreted as a 

disagreement or endorsement of the comment, the standard or its legal sufficiency.