ASTM E3260-21

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E3260 − 21 An American National Standard
Standard Guide for
Forensic Examination and Comparison of Pressure
Sensitive Tapes
This standard is issued under the fixed designation E3260; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope environmental practices and determine the applicability of
regulatory limitations prior to use.
1.1 This guide is intended as an introduction to other
1.6 This international standard was developed in accor-
standard guides for the forensic examination of pressure
dance with internationally recognized principles on standard-
sensitive adhesive tape. It is intended to assist individuals who
ization established in the Decision on Principles for the
conduct forensic tape analyses in their evaluation, selection,
Development of International Standards, Guides and Recom-
and application of tests that can be of value to their examina-
mendations issued by the World Trade Organization Technical
tions. This guide describes the construction and classification
Barriers to Trade (TBT) Committee.
of various tapes and the methods to develop discriminatory
information using an efficient order of testing. This standard
2. Referenced Documents
provides an overview and guidance on the strengths and
2.1 ASTM Standards:
limitations of various techniques used in the analysis and
D123 Terminology Relating to Textiles
comparison of pressure sensitive adhesive tapes. The goal is to
E1732 Terminology Relating to Forensic Science
provide a consistent approach to forensic tape analysis.
E2224 Guide for Forensic Analysis of Fibers by Infrared
1.2 The forensic tape examiner addresses concerns such as
Spectroscopy
sample size, complexity and condition of the sample, environ-
E2225 GuideforForensicExaminationofFabricsandCord-
mental effects, collection and packaging methods, and case/
age
investigation specific issues. These factors require that the
E2228 Guide for Microscopical Examination of Textile Fi-
forensic tape examiner choose test methods, sample prepara-
bers
tion schemes, testing sequences, and degree of sample altera-
E2917 Practice for Forensic Science Practitioner Training,
tion and consumption that are suitable to each specific case.
Continuing Education, and Professional Development
Programs
1.3 This standard is intended for use by competent forensic
E3085 Guide for Fourier Transform Infrared Spectroscopy
science practitioners with the requisite formal education,
in Forensic Tape Examinations
discipline-specific training (see Practice E2917, Practice
E3233 PracticeforForensicTapeAnalysisTrainingProgram
E3233), and demonstrated proficiency to perform forensic
2.2 Other Documents:
casework.
SWGMAT Guideline for Assessing Physical Characteristics
1.4 The values stated in SI units are to be regarded as
in Forensic Tape Examinations
standard. Other units of measurement are included in this
SWGMAT Guideline for Using Light Microscopy in Foren-
standard as applicable to industrial usage.
sic Tape Examinations
1.5 Some of the methods discussed in this guide involve the
SWGMAT Guideline for Using Scanning Electron
use of chemicals, temperatures, and radiation sources. This
Microscopy/Energy Dispersive X-Ray Spectroscopy in
standard does not purport to address all of the safety concerns,
Forensic Tape Examinations
if any, associated with its use. It is the responsibility of the user
SWGMAT Guideline for Using Pyrolysis-Gas Chromatog-
of this standard to establish appropriate safety, health, and
raphy and Pyrolysis-Gas Chromatography/Mass Spec-
trometry in Forensic Tape Examinations
1 2
This guide is under the jurisdiction of ASTM Committee E30 on Forensic For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Sciences and is the direct responsibility of Subcommittee E30.01 on Criminalistics. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Current edition approved Jan. 1, 2021. Published January 2021. DOI: 10.1520/ Standards volume information, refer to the standard’s Document Summary page on
E3260-21. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E3260 − 21
3. Terminology 3.2.15 machine direction, n—the direction of the tape that
runs the length of the tape.
3.1 Definitions:
3.2.16 migration, n—the movement over a period of time of
3.1.1 For additional terms commonly employed for general
an ingredient from one layer to another.
forensic examinations, see Terminology E1732.
3.2 Definitions of Terms Specific to This Standard:
3.2.16.1 Discussion—This often occurs in electrical tapes
3.2.1 adhesive, n—a material that holds two or more objects
where plasticizer in the polyvinyl chloride (PVC) backing
together solely by intimate surface contact.
“migrates” into the adhesive.
3.2.17 monoaxially oriented polypropylene (MOPP), n—an
3.2.2 additives,n—materialsthatareincludedinadhesiveor
oriented polypropylene film in which the polymer has been
backing formulations to increase overall volume, impart color,
stretched in only one direction during the manufacturing
or provide other desired properties.
process. Tapes with such films can be torn by hand.
3.2.3 backing, n—a thin flexible material to which adhesive
3.2.18 plasticizer, n—material added to plastics to impart
is applied.
flexibility by creating spaces between the polymer chains and
3.2.4 backsize, n—a layer applied to the top side of the
lowering the inter- and intra-chain attractive forces, allowing
backing. Its purpose is to coat and fill a porous surfaced
freer movement of the chains.
backingwithamaterialthatisinerttotheadhesiveformulation
to be used.
3.2.18.1 Discussion—Plasticizers are used in pressure sen-
sitivebackings(particularlyPVC)andsomeadhesivestolower
3.2.5 biaxially oriented polypropylene (BOPP), n—an ori-
the glass-transition temperature and allow use at sub-ambient
ented polypropylene film in which the polymer has been
temperatures.
stretched in both the machine direction and cross direction
3.2.19 pressure sensitive adhesive (PSA), n—an adhesive
during the manufacturing process. Tapes with such films
that consists of a polymeric base, usually with appropriate
cannot be torn by hand.
plasticizers and tackifiers. It can form an adhesive bond with
3.2.6 calendering, v—a method of producing adhesive tape
no physical or chemical change and with the application of
by pressing an adhesive to a backing material through a series
only slight pressure.
of heated rollers. The surface appearance depends on the type
3.2.20 pressure sensitive adhesive (PSA) tape, n—a combi-
of roller used.
nation of a pressure sensitive adhesive with a continuous
3.2.7 calendering marks, n—characteristic marks left on the
flexible backing (cloth, paper, metal, or plastic) or with a
backing material due to the manufacturing process.
backing and release liner.
3.2.8 cellophane, n—a thin, transparent sheet made of
3.2.20.1 Discussion—Use of the word “tape” in this guide
regenerated cellulose that can be used as a backing material in
refers to PSA tapes and their components.
tape products.
3.2.21 prime coat, n—a coating of adhesive-like material
3.2.9 cellulose acetate, n—a type of transparent film that is
found between the tape adhesive and backing that serves as a
used for tape backings.
bonding agent.
3.2.9.1 Discussion—A matte surface is used for write-on
3.2.22 reinforcement, n—fabric (scrim), glass filaments, or
tapes. Cellulose acetate is more moisture-resistant than cello-
plastic filaments added to tape to impart stability and strength.
phane.
3.2.23 release coat, n—a coating applied to the top side of
3.2.10 creped paper, n—paper that has small folds in it
the backing that provides ease of unwind and prevents delami-
giving it high stretch and conformability. Used in the backing
nation or tearing.
of masking tape (saturated paper tape).
3.2.24 scrim, n—a loosely-woven gauze-type fabric added
3.2.11 elastomer, n—a material that can be deformed but
to duct tape for reinforcement and to impart strength.
when the forces are removed it returns to its original form.
Serves as the base material for pressure sensitive adhesives. 3.2.25 scrim count, n—the number of warp yarns per inch
versus the number of fill yarns per inch.
3.2.12 exclusionary difference, n—a difference in a feature
or property between compared items that is substantial enough 3.2.26 tack, n—property of an adhesive that allows it to
formabondimmediatelywithasurfacewiththeapplicationof
to conclude that they did not originate from the same source.
only slight pressure.
3.2.12.1 Discussion—An exclusionary difference is statisti-
3.2.27 tackifier, n—low molecular weight organic material
cally supported when an appropriate statistical analysis shows
that is added to the adhesive base polymer to impart tack.
a result outside the range of what usually occurs when the
items originate from the same source. 3.2.28 thickness, n—distance from one surface of a tape,
3.2.12.2 Discussion—When a statistical analysis is not backing, or adhesive to the other, usually expressed in the
suitable, an exclusionary difference can be determined by United States as thousandths of an inch, or the industrial
expert judgment. vernacular as “mils” which represents thousandths of an inch
3.2.13 fill yarns, n—see weft yarns (filling). (that is, 1 mil = 0.001 in.).
3.2.14 flatback paper, n—smooth paper backing masking 3.2.29 warp, n—the yarn running lengthwise in a woven
tape (saturated paper tape). fabric. D123
E3260 − 21
3.2.29.1 Discussion—Warp fibers in a scrim fabric run ICPMS). These different techniques can provide complemen-
lengthwise in the machine direction of a reinforced tape. tary information and should be selected and employed in an
3.2.30 weft, n—the yarn running from selvage to selvage at order to obtain the most discriminating information consistent
right angles to the warp. with the laboratory’s capabilities.
3.2.30.1 Discussion—Weftyarnsruncrosswise,perpendicu- 5.4 Typically,atapeexaminationinvolvessearchingforand
assessing any differences in the comparison of questioned and
lar to the warp direction in the scrim fabric of reinforced tape.
known samples.The absence of exclusionary differences at the
Also known as fill yarns.
conclusion of an analysis suggests that the tape samples could
3.2.31 yarn, n—a generic term for a continuous strand of
share a common origin. The strength of the interpretation is a
textile fibers, filaments, or material in a form suitable for
function of the type or number of corresponding features, or
knitting, weaving, or otherwise intertwining to form a textile
both. The evaluation of tapes for class characteristics can
fabric. D123
associate known and questioned tapes to a group but not to a
3.2.31.1 Discussion—For the purposes of this guide, yarn
single, individual source. A physical fit of tape ends provides
refers to lengths of fiber reinforcement (for example, twisted
the highest degree of association between two tapes. These
staple fibers, filament fibers).
interpretations of forensic tape comparisons are valid for
determinations that are conducted via expert judgment, statis-
4. Quality Assurance Considerations
tical means, or a combination of the two approaches.
4.1 Aquality assurance program shall be used to ensure that
5.5 Questioned tape samples can also be submitted with a
analytical testing procedures and reporting of results are
request to identify possible product information, manufacturer,
monitored by means that include but are not limited to
and retailing sources, in an attempt to obtain investigative lead
proficiency tests, applicable instrument performance
information. Physical characteristics and compositional data,
verifications, and technical audits. General quality assurance
collected as described in this guide, can be used in technical
guidelines are found in “Trace Evidence Quality Assurance
inquiries to tape manufacturing companies, comparisons with
Guidelines”.
various brands of tape purchased at local commercial outlets,
5. Summary of Guide and for comparisons to samples in reference collections/
databases.
5.1 The analysis and comparison of tape evidence in the
forensic science laboratory can provide valuable information
6. Significance and Use
due to the variability of tape products. However, some classes
oftapeexhibitmorevariabilitybetweensourcesthanothers.In
6.1 This guide is designed to assist the forensic tape
general, the more complex the product (for example, duct
examiner in selecting and organizing an analytical scheme for
tape), the more features it has for comparison lending itself to
the analysis, comparison, and identification of tapes. The size
higher discrimination.
and condition of the sample(s) influences the choice of
analyticalscheme.Theevaluationandinterpretationofthedata
5.2 This guide provides an overview of techniques applied
for each technique is an important part of an analytical scheme
to the forensic analysis of tape components. The information
butitisoutsidethescopeofthisguide.Thesewillbeaddressed
contained herein is intended to assist the examiner in charac-
in other ASTM standards.
terizing and comparing evidentiary tape samples. The forensic
examinationoftapeencompassesthedeterminationofphysical
7. Sample Handling
construction and chemical composition of tape products. Gen-
eral information on product variability, construction, and
7.1 The potential for a physical fit between known and
composition is provided.
questioned samples shall be considered before selecting the
method of tape analysis. Care should be taken to preserve the
5.3 Whiletapeswithinaspecificclasscanappearsimilaron
a macroscopic level, differences can be found on further ends of the tape samples for physical fit analysis.
examination of the physical and chemical characteristics.
7.2 Tape evidence can be a source for other trace evidence
Methods for the analysis of tape include the examination of
(for example, hairs, fibers, paint, glass, and explosives), latent
physical characteristics both visually and microscopically,
print evidence, and DNA evidence. Different forensic disci-
polarized light microscopy (PLM), Fourier transform infrared
plines are often called upon to examine the same item of
spectroscopy (FTIR), Raman spectroscopy, pyrolysis gas
evidence. The order in which the examinations are conducted
chromatography-massspectrometry(PGC-MS),scanningelec-
should be resolved on a case-by-case basis. If another disci-
tron microscopy with energy dispersive X-ray spectroscopy
pline is chosen to examine the evidence prior to the tape
(SEM-EDS), X-ray fluorescence spectrometry (XRF), X-ray
examination, obtain an unaltered representative sample if
diffraction (XRD), microspectrophotometry (MSP), and laser
possible.
ablation-inductively coupled plasma mass spectrometry (LA-
7.3 Techniquestoseparatetapespecimensshouldbechosen
with care to minimize alterations in the chemical or physical
“Trace Evidence QualityAssurance Guidelines,” Scientific Working Group for
properties. Methods for separation include using warm air,
Materials Analysis, FBI Publication, Washington, D.C., 1999, available from:
liquid nitrogen, or appropriate solvents (for example, hexane,
https://archives.fbi.gov/archives/about-us/lab/forensic-science-communications/fsc/
jan2000/swgmat.htm#laboratory%20audits methanol) in concert with gentle physical manipulation.
E3260 − 21
7.4 The item of evidence should be preserved in a manner tape. There are numerous other types of tape that are less
that does not interfere with future testing. frequently encountered in case work.
9.1.1 Duct Tape:
8. Tape Construction
9.1.1.1 Duct tape, also referred to as poly-coated cloth tape,
consists of three basic components: the backing, the reinforce-
8.1 Each of the components listed below might not be a part
ment fabric, and the PSA. These components together deter-
of all classes of tape. The relevant components are discussed
mine a duct tape’s appearance, strength, and end use.
under each individual tape class. The primary components of
9.1.1.2 The backing, which is usually polyethylene, is
tape are the backing and the adhesive.
available in various colors. Duct tapes that are silver or gray
8.1.1 Backings:
commonly contain a small amount of aluminum to impart
8.1.1.1 The tape backing, or film, provides a support mate-
color. Other colors are created by adding colored pellets to the
rialfortheadhesive.Thereisawiderangeofmaterialsusedfor
molten polyethylene. Inorganic materials (for example, talc or
tape backings due to the vast number of commercial end uses
calcite) can be added to the backing to increase properties such
for tape. These materials include, but are not limited to:
aswaterrepellency,tearstrength,andopacity.Thebackingcan
polyethylene, polypropylene, polyvinyl chloride, saturated
consistofasinglelayerormultiplelayersofpolyethylene.The
paper, cellulose acetate, cloth, and polyester.
backing can also exhibit characteristics imparted during the
8.1.1.2 The backing itself can be multi-layered.
manufacturing process, such as calendering marks and stria-
8.1.1.3 Other materials that can be added to the backing
tions. Additionally, lettering or designs can be imparted onto
include stabilizers, fillers, colorants, plasticizers, fire retardants
the surface or underside of the polyethylene backing. These
and preservatives. Release coats, backsize, and primer coats
latter features are often best observed and described after
can also be applied to the backing and are thin layers that are
separation of the backing from the other tape layers present.
easily lost with use or can be difficult to separate and therefore
Each of these characteristics can serve as discriminating
are analyzed with the bulk of the backing material.
features and should be recorded.
8.1.2 Adhesives:
9.1.1.3 The adhesive formulation for duct tapes consists of
8.1.2.1 The formulation of PSAs consists of an elastomer to
anelastomertowhichtackifyingresinsandinorganicmaterials
which tackifier resins and inorganic materials are added.
are added. The elastomer is typically natural rubber (polyiso-
8.1.2.2 There are different elastomers used in PSAs. PSAs
prene) but could also be a mixture/blend of synthetic or natural
can contain one elastomer or a blend of several different
elastomers, or both. Other materials used as elastomers include
elastomers.
styrene-butadiene copolymer and styrene-isoprene copolymer.
8.1.2.3 Examples of elastomers used in PSAs include, but
are not limited to: natural rubber (polyisoprene), synthetic 9.1.1.4 The tackifying resin is typically a n-C that is used
polyisoprene, polybutadiene, polyisobutylene, styrene butadi- to make the elastomer “sticky” or impart tack. Inorganic
ene random copolymer, styrene isoprene block copolymer materials are added to an adhesive formulation to either
(SIS), styrene butadiene block copolymer (SBS), styrene increase the overall volume or to impart color. In duct tape
ethylene-butylene block copolymer, ethyl or butyl acrylate, adhesives,anyofthefollowingexamplescanbefound:calcite,
silicones, and neoprene. dolomite, kaolinite, talc, titanium dioxide (anatase or rutile),
8.1.2.4 Tackifying resins are blended with elastomers to and zincite.
lower the glass transition temperature, allowing freer move-
9.1.1.5 The reinforcement fabric in duct tape, known as
mentofthepolymerchainsandthusgivingPSAstheir“sticky”
scrim, is commonly constructed of cotton, polyester, or a blend
adhesive property. The tackifying resin is typically a n-C .
of these two materials. Reprocessed cellulose can also be
Silicone and acrylic PSAs do not require a tackifier. More
found. The scrim is generally manufactured as either a plain
costly silicone-based adhesives can be found in adhesive
weave or weft-insertion (having knit warp yarns and texturized
formulations of tapes that are manufactured for use in high
fill yarns). Woven yarns can be twisted (spun), texturized, or
temperatures or for chemical resistance.
filament in both the warp and fill directions.Variations of these
8.1.2.5 Inorganic materials are added to an adhesive formu-
are also observed. Refer to Guide E2225 for further discussion
lation to either increase the overall volume or to impart color.
on these types of fabrics and their analysis.
Such materials include calcite, dolomite, iron oxide, kaolinite,
9.1.1.6 Other components that can be present within a duct
talc, titanium dioxide (rutile or anatase), and zincite. In
tape product are a release coat and a primer coat.
addition, zincite can also function as an “accelerator,” or
9.1.2 Electrical Tape:
cross-linker, for rubber-based adhesives.
9.1.2.1 Electricaltape,alsoknownasvinyltape,findsusein
8.1.2.6 The adhesive can also be multi-layered.
applications that require heat resistance/retardance and insulat-
8.1.3 Reinforcing Materials:
ing properties. The two main components are the backing and
8.1.3.1 Reinforcing materials provide additional strength to
the PSA.
the tape. The materials used for the reinforcement can include
9.1.2.2 The backing of electrical tape is most commonly
fabric (scrim) and glass or plastic filaments.
made of PVC. Plasticizers, typically phthalate or adipate
compounds, are added to this material to impart flexibility to
9. Tape Classifications
the PVC. Other plasticizers can include alkyl/aryl phosphate
9.1 The classes of tapes most frequently encountered within compounds and dialkyl tin compounds. Backings vary in
forensic casework are duct tape, electrical tape, and packaging thickness and are commonly black in color, due to the addition
E3260 − 21
of carbon black. However, a variety of colored backings are release” formulations. Adhesives for saturated tapes are for-
produced and available. In addition to plasticizers, inorganic mulatedwithlesstacksincestrongadhesiontoasurfaceisless
materialssuchasleadstearate,leadcarbonate,antimonyoxide, desirable in masking applications. As with most tapes, if the
kaolinite, calcite, and titanium dioxide (anatase or rutile) can product is designed to endure exposure to high heat or
also be found. chemical reagents, the formulation is cross-linked to provide
9.1.2.3 The adhesive can be formulated in several ways, the needed strength.
9.2.2.4 Other components found within a paper tape can
depending on the intended end use, and can be either colorless
or black, due to the addition of carbon black. Adhesive include a backsize layer that is applied to the side of the
backing opposite the adhesive. There are a variety of materials
formulations typically consist of acrylic-based PSA or highly
cross-linked rubber-based PSA. The adhesive layer can also that are used for this purpose, such as acrylic and polyvinyl
contain plasticizers, either intentionally added by the manufac- acetate, and the material used depends upon the adhesive
turer or as a result of migration from the backing layer. formulation. In conjunction with the adhesive formulation, a
primer coat can be present.
9.1.2.4 Other components that can be present within an
electrical tape product are a release coat and a primer coat. 9.2.3 Filament/Strapping Tape:
9.2.3.1 Filament tapes are similar to packaging tapes in
9.1.3 Packaging Tape:
construction with the addition of reinforcement material. The
9.1.3.1 Packagingtapeisdesignedasageneral-purposetape
backingforthistypeoftapeistypicallyconstructedoforiented
used to seal packages. The two main components are the
polypropylene (low cost) or polyester (high cost). The rein-
backing and the PSA.
forcement filaments can be glass, nylon fibers, or polyester
9.1.3.2 Packaging tape backings are typically clear but also
fibers running in the machine direction. Adhesives found on
can be found in various shades of tan or brown. Polypropylene
such tape products can be colored or colorless. The elastomer
in the isotactic form is the most commonly encountered
is typically either isoprene or styrene-isoprene block copoly-
backing. Packaging tape backings can be subdivided into two
mer.
distinct types based upon their tear resistant properties: MOPP
9.2.4 Cloth Tape:
and BOPP. Polyester also can be used for packaging tape
9.2.4.1 Clothtapesaremostfrequentlyusedformedicaland
backings.
athletic purposes. Common cloth backing materials include
9.1.3.3 Packaging tape adhesives are typically clear but are
natural and synthetic woven cloth (for example, cotton, poly-
available in shades of tan or brown. Generally, when the
ester). Traditionally, adhesives were natural rubber-based, but
backing is colored, the adhesive is clear and vice versa. While
in recent history have been largely replaced by acrylic copo-
clear adhesives contain no inorganic material, the colored
lymers and other synthetic elastomers.
adhesivescancontaininorganicmaterialsuchasironoxideand
9.2.5 Offıce Tape:
titaniumdioxide.Adhesiveformulationstypicallyareisoprene-
9.2.5.1 Office or stationery tape is comprised of a backing
based, styrene-isoprene copolymer-based (SIS), or acrylic-
and a PSA. The most common tape backings include cellulose
based.
acetate, cellophane, and polypropylene and can range in
9.1.3.4 Other components that can be present within a
appearance from clear glossy or matte to a translucent yellow.
packaging tape are a release coat and a primer coat.
The PSAis typically isoprene-based, acrylic-based, or styrene-
9.2 Other Tapes:
isoprene copolymer-based. As mentioned in the previous tape
9.2.1 Othertypesoftapethatcanbeencounteredinforensic
discussions, a release coat and a primer layer can also be
casework include, but are not limited to, masking tape (satu-
present.
rated paper tape), filament/strapping tape, cloth tape, and office
tape.These tapes would be analyzed in a similar manner as the
10. Procedure
above-mentioned tapes.
10.1 Ascheme for forensic tape examinations is outlined in
9.2.2 Masking Tape:
Figs. 1-4. Potentially useful techniques for the discrimination
9.2.2.1 Masking tape, also known as saturated paper tape,
of tape backings and tape adhesives are listed. For any given
consists of a paper backing with a saturant and a PSA. This
comparison, not all the techniques listed in Fig. 1 are neces-
typeoftapeisusedasamaskingmaterialforpaintapplications
sarily required. Tape class, sample size, condition, and layer
and other general-purpose applications.
structure should be considered when determining which tech-
9.2.2.2 The backing of a paper tape is either flatback or
niques to use. The forensic tape examiner should use the most
creped paper that has been saturat
...