ASTM E1610-95(2001)
(Guide)Standard Guide for Forensic Paint Analysis and Comparison
Standard Guide for Forensic Paint Analysis and Comparison
SCOPE
1.1 This guide is intended to assist individuals and laboratories that conduct forensic paint analyses in their selection, application, and evaluation of tests that can be of value to their investigation. It is not intended as a detailed methods description or protocol for the analysis and comparison of paints but as a guide to a reasonable order for testing and to the strengths, limitations, and possible pitfalls of each of a variety of potentially useful analytical methods. Numerous detailed materials are available that discuss each method, and selected references are noted as appropriate.
1.2 This guide is intended for application to the analysis of industrial and commercially prepared paints and related coatings. It does not propose to address the unique requirements of artistic, historical, or restorative paint analysis, although some of the methods discussed herein may be applied to those fields.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
General Information
Relations
Standards Content (Sample)
Designation: E 1610 – 95 (Reapproved 2001)
Standard Guide for
Forensic Paint Analysis and Comparison
This standard is issued under the fixed designation E 1610; 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 (e) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Forensic paint sample analyses and comparisons are typically distinguished by a limited amount
sample that precludes the application of standard industrial paint analysis procedures or protocols to
these analyses. The issues before a case or investigation, sequence of events at the scene in question,
sample size, complexity and condition, environmental effects, and collection methods generally force
a criminalist to address the issues of test choice, sample preparation scheme, test sequence, and degree
of sample alteration and consumption that are efficacious to each specific case as well as the interests
of all parties to a litigation.
1. Scope from Instrumentally Measured Color Coordinates
D 3168 Practice for Qualitative Identification of Polymers
1.1 This guide is intended to assist individuals and labora-
in Emulsion Paints
tories that conduct forensic paint analyses in their selection,
D 4764 Test Method for Determination by X-Ray Fluores-
application, and evaluation of tests that can be of value to their
cence Spectroscopy of Titanium Dioxide Content in Paint
investigation. It is not intended as a detailed methods descrip-
E 105 Practice for Probability Sampling of Materials
tion or protocol for the analysis and comparison of paints but
E 141 Practice for Acceptance of Evidence Based on the
as a guide to a reasonable order for testing and to the strengths,
Results of Probability Sampling
limitations, and possible pitfalls of each of a variety of
E 275 Practice for Describing and Measuring Performance
potentially useful analytical methods. Numerous detailed ma-
of Ultraviolet, Visible, and Near —Infrared Spectropho-
terials are available that discuss each method, and selected
tometers
references are noted as appropriate.
E 308 Test Method for Computing the Colors of Objects by
1.2 This guide is intended for application to the analysis of
Using the CIE System
industrial and commercially prepared paints and related coat-
E 334 Practices for General Techniques of Infrared Mi-
ings. It does not propose to address the unique requirements of
croanalysis
artistic, historical, or restorative paint analysis, although some
E 380 Practice for Use of the International System of Units
of the methods discussed herein may be applied to those fields.
(SI) : the Modernized Metric System
1.3 This standard does not purport to address all of the
E 805 Practice for Identification of Instrumental Methods of
safety concerns, if any, associated with its use. It is the
Color or Color-Difference, Measurement of Materials
responsibility of the user of this standard to establish appro-
E 860 Practice for Examining and Testing Items that Are or
priate safety and health practices and determine the applica-
May Become Involved in Products Liability Litigation
bility of regulatory limitations prior to use.
E 1360 Practice for Specifying Color by Using the Optical
2. Referenced Documents Society of America Uniform Color Scales System
E 1492 Practice for Receiving, Documenting, Storing, and
2.1 ASTM Standards:
Retrieving Evidence in a Forensic Science Laboratory
D 16 Terminology for Paint, Related Coatings, Materials,
E 1508 Guide for Quantitative Analysis by Energy-
and Applications
Dispersive Spectroscopy
D 1535 Practice for Specifying Color by the Munsell Sys-
tem
3. Terminology
D 2244 Test Method for Calculation of Color Differences
3.1 Definitions—For definitions of terms used in this guide,
see Terminology D 16.
This guide is under the jurisdiction of ASTM Committee E30 on Forensic
Sciences and is the direct responsibility of Subcommittee E30.01 on Criminalistics.
Current edition approved March 15, 1995. Published September 1995. Originally Annual Book of ASTM Standards, Vol 14.01.
published as E 1610 – 94. Last previous edition E 1610 – 94. Annual Book of ASTM Standards, Vol 14.02.
2 5
Annual Book of ASTM Standards, Vol 06.01. Annual Book of ASTM Standards, Vol 03.01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E 1610
3.2 Definitions of Terms Specific to This Standard: films with layers >20 μm in thickness and for the identification
3.2.1 discriminate—to distinguish between two samples of pigment elemental components of Z > 6, elemental concen-
based on differences; to differentiate. trations of >1 %, and paint vehicle components in excess of
3.2.2 discriminating power—the measure of an analytical 5 % by weight. These constraints are imposed by microscopi-
procedure is the ability to distinguish between two items of cal, infrared absorbance and energy dispersive X-ray analysis
different origin. system constraints.
3.2.3 known, , adj—an item of established origin.
6. Test Specimens
3.2.4 questioned, , adj—for the purpose of classification.
6.1 Suitable Known Specimens:
3.2.5 significant difference—a difference between two
6.1.1 Known paint specimens should be collected from
samples that establishes different origins for the two samples.
areas immediately adjacent to the point, or points, of transfer.
4. Summary of Practice
The point of impact or pressure transfer typically exhibits bare
substrate or substrate with a damaged paint film. The collected
4.1 Paint films are characterized by a number of physical
known specimens should contain all paint layers of the
and chemical features such as the following: color, surface
undamaged paint film. Paint layers can begin and end as well
texture, contamination, and weathering; striae due to wear,
as exhibit substantial variations in thickness over short dis-
impact, application techniques, or underlying surface irregu-
tances across a painted surface. This is particularly true in
larities; and paint layering order and thickness, presence of
automotive and architectural paint films at curves, corners, and
pigments or dyes, or both, and vehicles or resins and modifiers
edges, which are often impact or fulcrum points that may have
in the paint. These features can be determined and evaluated by
been subject to previous damage, sanding, or overpainting.
a variety of visual, macro and microscopical, chemical, and
6.1.2 The substrate or parent surface underlying the sus-
instrumental methods. Limited sample size and sample preser-
pected transfer area should be included in the sample collected
vation requirements dictate that these methods be selected and
when possible. Adjacent sections of wallboard, ceiling por-
applied in a reasonable sequence in order to maximize the
tions, door and window frames, implement handles, doors,
discriminating power of the test results.
fenders, hoods, or entire automobiles are examples of items
4.2 Searching for significant differences between samples is
that can be valuable. A few minutes of comparative work with
the objective of forensic paint analysis and comparison. Dif-
the parent surface(s) might resolve the questions in a case and
ferences almost always exist between samples. A forensic paint
save considerable time spent on other forms of laboratory
analyst’s goal is to demonstrate which differences are signifi-
cant. The absence of significant differences at the conclusion of analysis.
6.1.3 Simple scraping may not provide suitable materials
an analysis is taken as evidence of common origin. The
likelihood of common origin between specimens is a function for definitive comparison. Paint flakes containing all layers can
be removed from the parent surface by a number of methods,
of a number of factors, including the following: the type or
including deformation by impact to the opposite side of the
number, or both, of matching features; the type of components
surface, by lifting particles already separated from the surface
in the paint film; the presence or absence of studies quantifying
but still retained at one edge or prying up fragments using a
the uniqueness of these components; and the discriminating
tool that does not contaminate. It is important that the blade be
power of the test methods used.
inserted down to or adjacent to the parent surface and the paint
4.3 The test procedure selected in a paint analysis and
popped from the surface with the latter technique.
comparison generally begins with careful sample documenta-
6.2 Suitable Questioned Specimens:
tion. Some features of that documentation are described in
6.2.1 Questioned specimens should include all loose or
Practices E 380, E 860, and E 1492. This documentation is
transferred paint material available at the scene in question.
usually followed by the development of an evidence sampling
The scene can include such items as tools, floors, walls, glass
plan. Such plans are discussed in Practices E 105 and E 141.
fragments, hair, fingernails, a roadway, adjacent structures,
Although these practices are directed toward industrial and
transfers or smears on vehicles, or transfers to or from
consumer product sampling environments, they offer some
individuals such as damaged fabric with paint inclusions and
insight into the legal expectations in evidence sampling.
fibers or fabric impressions on painted surfaces. Items with
Analysis generally proceeds with the simplest nondestructive
paint transfers should be packaged and submitted in their
tests available for the conditions of the case once sampling and
specimen documentation are complete. If these initial tests do entirety for examination whenever possible, rather than at-
tempting to remove paint from a substrate in the field.
not discriminate between the samples, the examination will
continue with other tests that can require an increasing degree Representative or partial sampling can reduce or even elimi-
nate the possibility of a conclusive comparison or physical
of sample preparation or consumption and are selected based
match to known materials.
on the sample availability, and tests’ potential for discriminat-
6.2.2 Flasks of whole paint films or films still attached to a
ing the samples.
substrate, such as a painted piece of wood or metal, provide the
5. Significance and Use
most useful questioned samples for analysis. Fragments of
5.1 The guide is designed to assist in selecting and organiz- films that do not represent the complete layering structure of
ing an analytical scheme for identifying and comparing indus- the original surface obviously offer fewer characteristics for
trial, architectural, or automotive paint films. comparison but can be useful in physical fits and other
5.2 The techniques discussed are generally applicable to examinations.
E 1610
6.2.3 Smeared or abrasively transferred samples are gener- discussed at this point in the guide, it is an essential part of all
ally more difficult to analyze but may provide useful informa-
steps in an analysis. The resulting notes should be sufficient to
tion. Smeared transfers can exhibit pigment and vehicle min- substantiate the conclusions reached in the criminalist’s report.
gling from several paint layers or films that could preclude
7.5 Physical Match:
application of some of the analytical methods discussed in this
7.5.1 The two most specific comparisons that can be made
guide. Paint scraping can sometimes be used to recover
between otherwise visually similar paint specimens involve the
specimens of material transfers to surfaces or questioned
matching of known and questioned sample edges for a physical
specimens of smears.
fit, or matching the surface striae on the underside of a paint
fragment to those on a parent surface, or both. This statement
7. Procedure
assumes that the edges in question exhibit comparable details
7.1 Discussions of forensic paint analysis are provided in
such as changes in fracture direction or that the parent surface
dated but detailed form by Crown (1) , more recently by
exhibits unique striae.
Raaschou (2), and Thornton (3), and Maehly and Strömberg
7.5.2 Uniqueness is sometimes difficult to document, and
(4). The general analytical flow of an idealized paint sample
comparative photography or phototransparency overlays may
analysis is shown in Fig. 1. The major steps in Fig. 1 are
be needed to illustrate the physical match.
numbered to correspond to the discussions presented in this
7.6 Analysis of Paint Layers:
guide (that is, 7.8, Solvent Tests).
7.6.1 Paint layers in a paint film are generally identified by
7.2 The flow path of Fig. 1 is structured to encourage use of
the more specific and least evidence-consuming tests such as microscopical viewing of specimen edges at 5 to 100 power
magnification. The more obvious layers are generally visible
edge matching or striae matching, prior to tests that require
more manipulation, preparation, or consumption, or some without sample preparation. The unprepared fractured samples
are suitable for preliminary characterization and solvent/
combination, of samples.
7.3 Fig. 1 should not be construed to imply that other solubility examinations. Definitive paint layer identification
examinations are of no use or that the order of the procedures
usually requires the on-edge mounting and polishing of paint
in the flow chart is irrevocable. It is simply presented as a samples to #3-μm finish. Surface finish needs to approach the
logical progression upon which to base the following discus-
finest pigment particle size in a sample if similarly colored
sion. Virtually any other flow could be used once the possibility layers are to be distinguishable. This preparation can be carried
of physical fits of edges or striae is eliminated and the
out at an initial point in the analysis or reserved until later tests,
specimen size is adequate. as long as the criminalist considers the initial layer count of an
7.4 Specimen Descriptions:
unprepared edge to be only preliminary. Discussion of these
7.4.1 The initial steps in a forensic paint analysis are the
later tests begins in 7.13. Loosely bonded or delaminated layers
visual and macroscopical evaluation, description, and docu-
can also be identified at this point, without additional prepara-
mentation of the evidence specimens’ original condition. This
tion, and noted for further observation during subsequent
can also occasionally be the final step in an analysis if
analysis.
significant differences in the specimens are identified during
7.6.2 Thin sections of paint film fragments, prepared either
the initial evaluation.
manually or by microtomy, can be mounted for viewing by
7.4.2 The initial evaluation should include a critical review
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