MADLEN MARGAU and

GERRI LYNN VARDY

Centre of Forensic Sciences,

Chemistry Section,

Toronto, Ontario, Canada

madlen.margau@ontario.ca

THE ANALYSIS OF BLACK

ELECTRICAL TAPE AS

FORENSIC EVIDENCE

Outline Case Example

Electrical Tape Analysis

Characterization and Discriminating Power

Physical Properties

Chemical Composition

Fourier Transform Infrared Spectroscopy (FTIR)

Pyrolysis Gas Chromatography – Mass

Spectrometry (PGC/MS)

Scanning Electron Microscopy – Energy

Dispersive X-ray Analysis (SEM/EDX)

X-Ray Diffraction (XRD)

Laser Ablation-Inductively Coupled Plasma-Mass

Spectrometry (LA-ICP-MS) preliminary work

Toronto “Letter Bomber” Adel Arnout, August 2007

3 bombs sent to roommate, handyman, lawyer

Electrical tape comparisons provided link between bombs

sent and Arnout’s residence

Case Example

Can we discriminate between electrical tapes?

Recent Electrical Tape Studies

A. H. Mehltretter et. al.

Journal of Forensic Sciences, 2011 p82-94.

85% discrimination based on analysis of

adhesives

J. V. Goodpaster et. al.

Journal of Forensic Sciences, 2007 p610-629.

Journal of Forensic Sciences, 2009 p328-338.

Do these studies apply to electrical tapes available in Ontario?

Surface Texture

Width and Thickness

Adhesive

Backing

Plasticizer

Physical Properties

FTIR

PGC/MS

XRD

SEM/EDX

Adhesive

Plasticizer

Backing side

Adhesive

Backing

Electrical Tape Analysis

78 Electrical Tapes obtained in Southern Ontario

from stores and households

Tapes were analyzed and compared

Tapes grouped by chemical properties

Tapes further discriminated by physical properties

Electrical Tape Analysis

Country No of

Tapes

No of

Brands

MANUFACTURER

Taiwan 47 10 3

USA 16 4 1

China 14 9 3

Unknown 1 - -

3

COUNTRIES

78

TAPES

23

LISTED

BRANDS

7

LISTED

MANUFACTURERS

These Tapes Were Not Manufactured in Canada

Electrical Tapes

PVC Tapes

Clear

Adhesive

Rubber TapesClear

AdhesiveAcrylic

AdhesiveTalc in backing

Black

Adhesive Unable to

identify

adhesive

Adipate Plasticizer

in backing

Butadiene

Isoprene

Styrene

Adhesive

•Calcite,

•Aragonite

•Combination

•None

Filler in

backing

•Phthalate

•Adipate

•Phosphate

Ester

•Mixture

Plasticizer

in backing

Fourier Transform Infrared

Spectroscopy (FTIR)

Collection time: Wed Dec 29 11:01:00 2021 (GMT-05:00)

Sample: CFS TAPE SAMPLE 132 ADHESIVE SIDE

Number of sample scans: 1Number of background scans: 0Resolution: UnknownSample gain: 1.0Optical velocity: 0.0000Aperture: 0.00

Comments:

BLD: CNM: AWCPY: DPM: EXP: G_GATE.XPMLCT: SFM: Golden GateSNM: CFS TAPE SAMPLE 132 ADHESIVE SIDEXPP: C:\OPUS_65\XPMIST: OK

69

9

74

1

83

790

9

96

5

10

39

10

71

11

22

12

70

13

76

14

53

15

39

15

80

16

00

17

28

28

60

29

18

29

55

-0.15

-0.10

-0.05

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

0.60

0.65

Arb

itra

ry u

nits

500 1000 1500 2000 2000 2500 3000 3500 4000

Wavenumbers (cm-1)

FTIR

Butadiene Isoprene Styrene

Phthalate Plasticizer

PVC Tapes

Clear

Adhesive

Black

Adhesive

•Adipate

•Mixture Plasticizer

•Butadiene Isoprene Styrene

•Butadiene Styrene (Polyterpene)Binder

•Butadiene Isoprene Styrene

•Butadiene Isoprene Styrene AcrylicBinder

•Phthalate

•Adipate

•Phosphate Ester

•Mixture

Plasticizer

Pyrolysis Gas Chromatography –

Mass Spectrometry (PGC/MS)

PGC/MS RT: 0.00 - 32.51

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32

Time (min)

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Relat

ive A

bund

ance

NL:9.91E7

TIC MS ETape94Butadiene

● Isoprene

● Methyl Methacrylate

● Styrene

● D-Limonene

● Dioctyl Phthalate

●

●

●

●

●

RT: 0.00 - 32.53

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32

Time (min)

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Relat

ive A

bund

ance

NL:6.13E8

TIC MS Etape191r

●

●

●

●

PVC Tapes

•Calcite

•Aragonite

•Rutile

•Anatase

•Talc

FillerFlame

Retardant

Clear

Adhesive

Antimony

Oxide

in some

•CalciteBlack

Adhesive

Antimony

Oxide

in all

X-Ray Diffraction (XRD)

10 20 30 40 50 60 70 80

Two-Theta (deg)

0

500

1000

1500

2000

2500

3000

3500

Inte

nsity(

Co

un

ts)

[112-R1.raw] SS#7

[119-R1.raw] SS#14

X-Ray Diffraction (XRD)

● Calcite

Antimony Oxide

●

●

●●

●

●●

●

●

●●●

200 µm200 µm

Scanning Electron Microscopy (SEM)

Surface features on tape backings

PVC Tapes

Major Elements Present

Note Cl present in all tapes

Backings of

Clear Adhesive

Tapes

Al Si

Al Sb

Al Si Ca

Al Si Ca Ti

Al Si Ca P

Al Si Sb

Al Ca Sb

Al Ca Pb

Al Ca Ti

Al Ca Sb Ti

Sb

Backings of

Black Adhesive

Tapes

Mg Al Sb

Mg Al Sb Ca

Energy Dispersive X-Ray Analysis (EDX)

100 µm

100 µm100 µm

100 µm

Microscopy

78 Electrical Tapes

FTIR 10 Groups

3003 pair-wise

comparisons

Results

Discriminated 2955 pairs

98% Discriminated

PGC/MS 15 Groups

Physical Properties 48 Groups

XRD 33 Groups

36 GroupsSEM/EDX

Results

Distinguished all tapes from different manufactures

Distinguished all but 3 pairs of tapes from different

brands - indistinguishable pairs are from the same

manufacturer

Distinguished some tapes of the same brand

Distinguished 1 out of 6 tapes in a multipack

No of

Tapes

No of

Groups

BRAND MANUFACTURER

37 22 Avatach Co. Ltd.

(4, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1)

Tartan 3M (5, 1, 4, 1, 1, 1)

Cantech/Tartan 3M (2)

Temflex 3M (1, 1)

Nappa Ultra Pro (1)

Nexxech (1)

Avatack Co. Ltd.

8 5 Globe (3, 1, 1)

Titan, Futurchem (2)

Bluejay (1)

Achem Technology

Corporation

2 2 Nasco (1,1) New Age Supply

Company

Results - Taiwan

No of

Tapes

No of

Groups

BRAND MANUFACTURER

12 5 Super 33+ (3, 2)

Scotch 3M 700 (3, 1)

Super 88 (3)

Scotch 3M, USA

4 2 Linerless Rubber Splicing

Tape (3, 1)

Scotch 3M, USA

Results - USA

No of

Tapes

No of

Groups

BRAND MANUFACTURER

8 5 Home Electric/T4 ProFlex (3)

T4 ProFlex (2)

Home Electric (1, 1)

Cefco (1)

Hebei Huaxia

Enterprise Co.

3 3 Home-Aide (1)

Nobility (1)

Three Star (1)

N/A

2 2 Premium 85 (1)

Revere 7 (1)

Plymouth

1 1 Duck (1) Henkel

Results - China

Results – Unknown Tape

No of

Tapes

No of

Groups

BRAND MANUFACTURER

1 1 Unknown (1) Unknown

Laser Ablation-Inductively Coupled Plasma-

Mass Spectrometry (LA-ICP-MS)

Analyzed 8 elements

Raster scan over 1x1 mm area of PVC backing

Preliminary data anlaysis

± 40%

Analyzed and compared 54 PVC tape backings

1431 pair-wise comparisons

Reproducibility studies

LA-ICP-MS

Preliminary Analysis

Element

% of pairs

discriminated for

54 PVC tapes

49Ti 91

27Al 90

25Mg 87

42Ca 87

207Pb 87

208Pb 87

68Zn 83

121Sb 77

123Sb 78

137Ba 64

LA-ICP-MS

Isotopes Analyzed

Preliminary Results - 99.4% of Tapes Discriminated

LA-ICP-MS

4 Groups of indistinguishable

Electrical Tapes

(2, 2, 2, 2)

Preliminary results are promising!

More work needs to be done!

Multipacks

Same brand

Different brands, same

manufacturer

12 Groups of tapes indistinguishable

by other techniques

(4, 3, 3, 3, 2, 2, 2, 2, 2, 2, 2, 2)

LA-ICP-MS

Preliminary Results

National Institute of Justice (NIJ)

Federal Bureau of Investigation (FBI)

Chu Jun Wei (University of Toronto student)

Centre of Forensic Sciences

Alex Heydon, David Ruddell (LA-ICP MS)

Linda Morrison (PGC/MS)

Matthew Gibb (XRD)

Dale Randall, Elspeth Lindsay (SEM/EDX)

Cara Shepard

Acknowledgments

Questions?