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>> Okay our next speaker will be Madlen Margau from the Center
of Forensic Sciences in Toronto, Canada,
and she's gonna be speaking on "The Analysis
of Black Electrical Tape as Forensic Evidence".
[ Pause ]
>> Good afternoon everyone.
So I'll be speaking about the analysis
of black electrical tape today.
This work was done by my-- was interpreted by myself
and Gerri Lynn Vardy at the Center of Forensic Sciences.
This is a lab that services the province of Ontario in Canada
and it's the second-- Ontario is the second largest province
with a population 13 million people.
We have two laboratories, one in Toronto
and a smaller lab in Sault Ste.
Marie that services the northern part of the province.
By talking about an example
where we encounter black electrical tape as evidence
and this is what began our study of the electrical tapes.
I'll talk about how we do electrical tape analysis
and characterization using physical properties
and the chemical--
and determination
of the chemical composition using the standard techniques
available to us in our laboratory:
Fourier Transform Infrared Spectroscopy,
Pyrolysis Gas Chromatography-Mass
Spectrometry, Scanning Electron Microscopy -
Energy Dispersive X-ray Analysis, and X-Ray Diffraction.
And lastly, I'm gonna talk about some preliminary work looking
at electrical tape backings
by Laser Ablation-Inductively Coupled
Plasma-Mass Spectrometry.
In August 2007, there were three bombs, either sent
or delivered to-- at the time it seemed
like three random people-- random unrelated people.
It turned out that these three people according Adel Arnaout
who was the person who sent the bombs had wronged him
in some way.
One person was a previous roommate,
one person was a handyman that had also evicted had--
who had evicted Adel Arnaout, and one was a lawyer
who had represented him
in a criminal charge in a previous case.
In this case, we had looked at--
there was several pieces of evidence submitted to the center
for analysis including multiple types of tape.
The electrical tape in that--
the electrical tape from the 3 bombs sent were compared back
to a roll of tape at Arnaout's residence,
and these provided a link.
The tape-- the tape from the bombs were indistinguishable
in physical properties and chemical composition to the roll
of tape at Arnaout's property-- residence.
One of the questions that came up in the preliminary hearing
in this case was our ability to distinguish
between black electrical tapes and this is when we decided
to do the-- to do a study of our own to see how discriminate--
how much discrimination we can get.
And I do wanna mention some recent studies
that have been published.
One by the FBI where they are able to--
where they found that they could discriminate--
they had a 85 percent discrimination based
on the adhesives of--
of electrical tapes alone
with further discrimination looking at their backings.
And Goodpaster has published studies looking
at the discrimination based
on surface features, SEM/EDX, and FTIR.
And one of the questions is, are studies done
in other countries relevant to the tapes
that we have available to us in Ontario?
The way we do our electrical tape analysis is we start
with the physical properties, we'll look at--
we'll do microscopy, we'll look at surface texture,
we'll measure width and thickness.
We do FTIR on the adhesives, backings
and we extract the plasticizers
from the adhesives using a solvent
and we'll analyze that as well.
We look at the adhesives and plasticizers using PGC/MS.
For this study we didn't look at the backings
but we would in-- in-- in case work.
We did XRD of the backing side of the tapes and we looked
at SEM/EDX of both the adhesive and the backing.
In case work we would look at physical properties first.
In our case, due to the number-- large number of comparisons,
we looked at physical properties last.
We collected 78 tapes, we went out to hardware stores,
discount stores, electrical stores
and we also got tapes donated from households and we went--
some of the stores we went to multiple locations
and we purchased every type of electrical tape they had.
We analyzed and compared these tapes.
We first grouped them by chemical properties and then
by physical properties.
Where were these tapes manufactured?
The largest group was manufactured in Taiwan
and there are three manufacturers divided
into ten brands.
One manufacturer in the United States, Scotch 3M,
we had 16 tapes and 4 brands
and at least three manufacturers in China.
Not all the manufacturers were listed on the tapes from China,
and there are 14 tapes and 9 brands,
and then there is one tape
where we did not have the manufacturer's information
but that particular tape, we were able
to distinguish from all the others.
One thing to note is none of these tapes were manufactured
in China which does indicate to us
that it is an international market and the results
of other studies would be relevant to the tapes
that are available to us.
I'll go through-- I'll first go through the different techniques
and then at the end I'll go through the results
that we obtained, so for the polyvinyl chloride backed tapes
they were first divided into tapes
of clear adhesives and black adhesives.
The adhesives were generally butadiene, isoprene, styrene,
and they had a combination of fillers calcite, aragonite,
a combination of the two or none seen by IR and they also had--
they all had-- plasticizers either phthalates, adipates,
two samples had phosphate esters and some
of the samples had mixtures.
The black adhesives due to the high loading of carbon black,
it was difficult to identify the type of adhesive
but we were further-- we were later able
to identify the adhesives using Pyrolysis Gas Chromatography
and most of these-- all of these had adipate plasticizers.
Four of the samples that we had and these are manufactured
in 3M had rubber backed adhesives-- a rubber backed--
were rubber backed tapes, not PVC backed tapes.
These ones had clear adhesives that were acrylic and talc
in the backing, we were not able
to further discriminate these four tapes chemically,
one tape had a different width, so I'm not--
I'm gonna focus my discussion on the PVC tapes.
And here's an example to show you two--
a spectra of two tapes that we were able to put in--
that we discriminated against.
So you could see-- in the--
in the area that's circled in the red there's a peak
at 15-39 that's present in the top spectra,
and not on the bottom and then there's a doublet
at around 13-70 that's present at the bottom--
in the bottom spectra and there's only a singlet
in the top spectra and that's
from the tack-- from the tackifier.
In P-- in using PGC/MS, we were able to--
for the clear adhesives we saw
that we had butadiene isoprene styrene,
and we also saw small amounts of an acrylic component
which we did not see by IR, and it gave us more information
about the plasticizers that were present namely the minor
components, again, that we didn't--
weren't always able to see by IR.
For the black adhesives, we were able
to determine what those were butadiene isoprene styrene,
and butadiene styrene with a polyterpene tackifier.
>> And the plasticizers again, it gave us more information
about the minor components that were present with the adipates.
And here are two chromatograms and you could see the--
again, these were two tapes that we were--
that we differentiated, the top one has more isoprene
as compared to butadiene and the bottom one has more butadiene
as compared to the isoprene.
The top chromatogram also has the acrylic component methyl
methacrylate and they both have styrene--
D-Limonene and phthalate plasticizer.
X-ray diffraction for the tapes with the clear back--
with the clear adhesives, we saw antimony oxide
which is a flame retardant, it was present in some of the tapes
and then we saw a combination of the fillers so calcite
and aragonite forms of calcium carbonate,
rutile and anatase forms of titanium dioxide and talc.
And for the tapes with the black adhesives, we saw antimony oxide
in all of the tapes and calcite in some.
And here are two diffraction patterns,
top one has more antimony oxide compared to calcite,
and the bottom has more calcite compared to antimony oxides,
so these both have the same components
but they're present in different amounts.
The surface features we could see using Scanning Electron
Microscopy, the surface features are present on the tapes
from the manufacturing process as well as from the pigment size
of the fillers at the-- maybe--
may have been added to the backings.
The tape on your left is less rough, and the tape
on the right has more features as well as at the oval pits
which are present from the manufacturing process
or calendering marks.
Energy dispersive x-ray analysis,
for the clear back tapes we had a combination
of different elements present in these tapes
and this data is just for the backings but we did look at EDX
of the adhesives as well.
And I just listed the main elements present,
some of the minor ones are not listed here
so you could see there's a lot of variability, and the backings
of the black adhesives had less variability
in the elements present.
These are photo micrographs taken through a video camera
on the Laser Ablation ICP-MS and you could just see the features
of the backings and how they vary
so the top two tapes have calendering marks
and then the bottom two tapes have different amounts
of surface roughness.
Our results for the 78 electrical tapes analyzed
which represents three thousand and three pairs,
we were able to-- we first grouped those tapes
into 10 groups according to FTIR.
We can then compared each of the tapes within those 10 groups,
and we looked at the PGC/MS for the tapes within each
of those 10 groups and were able
to further break those ten groups down into 15 groups.
We then looked at each of the tapes in those 15 groups
and we looked at the XRD results of those groups and were able
to further break those 15 groups down into 33 groups
and then we looked at the elemental composition
from SEM/EDX of each of the 33 groups and were able to break
that down into another 36 groups.
So that's for the chemical composition
and then lastly we looked at the physical properties, microscopy,
thickness and width, and were able
to further separate those 33 groups--
36 groups into 48 groups.
So that-- our overall results, we're able to--
discriminate 2955 of the 3003 pairs
which gives us a 98 percent discrimination.
How does that relate back to the brands?
We were able to discriminate all the tapes
from the different manufacturers.
We're-- distinguished all but three pairs of tapes
from different brands, distinguished some tapes
of the same brand, and one tape out of--
one out of six tapes in a multipack
and this multipack was a rainbow multipack of ten tapes
which had another four-- four colored tapes.
So we were able to distinguish one of the--
there were six black tapes within this multipack
and we were able to distinguish one
of those black tapes from the other five.
And how does this relate back to the specific brands?
So our largest group manufactured in Taiwan,
there were 37 tapes manufactured Avatack Company that was broken
down into 22 groups and they were--
that had between one and five tapes,
the ones in blue are the multi-packs
and then there is Cantech, one group that had Cantech
and Tartan 3M tapes which we were not able
to discriminate from each other.
Then Achem Technology Corporation, we were able
to divide those eight tapes into five groups and we were able
to distinguish the tapes from New Age Supply Company.
From the tapes manufactured in the USA, 12--
the 12 PVC tapes were broken down into five groups
and we were able to distinguish some of the same brands,
and then the four tapes with the-- that were--
had the rubber back-- the rubber backing we are able to break
down into two groups and our last-- last country--
tapes manufactured in China, Hebei Huaxia,
there was one group that had Home Electric
and T4 ProFlex tapes that we were not able to distinguish
from each other but we were able
to distinguish other T4 ProFlex tapes and Home Electric tapes.
And then we were able to distinguish the rest
of the tapes manufactured in China,
and then there was the one unknown tape
that we didn't have manufacturer's information for.
So I'm gonna spend the last bit of my talk talking
about the elemental composition
from Laser Ablation-Inductively Coupled Plasma Mass
Spectrometry, so this is a technique
that allows the determination of elemental composition
at the PPM levels of multiple elements
and again this is preliminary work that we've done.
So we analyzed 8 elements, two isotopes of--
eight elements and two of those elements we looked
at two isotopes for lead and antimony.
We did a raster scan over a one by one millimeter area
of the PVC backing, and for our preliminary data analysis,
we used a criteria of plus or minus forty percent.
We analyzed 54 of the 78 electrical tapes
and that represents 1431 pair-wise comparisons.
And we did some initial reproducibility studies,
so for number of tapes we did repeat measurements.
For one particular tape, we looked at 17 samples
from that tape, and one where you applied the plus
or minus forty percent criteria, only-- there-- there were two--
two pairs that were falsely discriminated based
on only one element, zinc.
We compared the results for the 54 tapes, the titanium was able
to give discrimination of 91 of the tapes, aluminum 90 percent,
magnesium, calcium and lead 87 percent, zinc 83 percent,
antimony 78-- 77 to 78 percent, and barium was 64 percent.
Overall, we had a 99.4 discrimination based
on the electrical tape backings.
>> We wanted to see how this related to our groups of--
and tapes that we were not able to indistinguish--
that we're not able
to distinguish using other techniques
so we had twelve groups of tapes that were indistinguishable
by the previous techniques.
Once we did Laser Ablation ICP-MS on those tapes and some
of which were multipack, same brand and different brand.
We were able to further discriminate eight groups
and we were left with four indistinguishable groups.
Three of those groups were multipacks and one was
of the same brand, the result
that surprised us the most was discriminating the multipack
of four tapes and again that multipack of four tapes was part
of a rainbow pack that had six color tapes in that pack
so I'm not sure how that rainbow pack was assembled
and whether those four tapes were actually
from the same batch or not.
Most of these discriminations were done based on more
than one element, two
of the pairs were discriminated based only on one element.
The preliminary results looked very promising.
A lot more work needs to be done on interpretation
and to ensure we don't have any false inclusions
or false discriminations so really looking
at more reproducibility studies.
I would like to thank NIJ and FBI for holding this conference
and for sponsoring my attendance.
This project was started
by an undergraduate student Chu Jun Wei
at the University of Toronto.
I'd like to thank the Centre of Forensic Sciences
for supporting research and then a number of people
that were involved in obtaining the data and helping ***--
interpret the data, and thank you.
[ Applause ]