TOYOTA EXHIBIT 2013
`
`Reactive Surfaces Ltd. LLP v.
`Toyota Motor Corporation
`IPR2016-01914
`
`

`

`DISCLAIMER
`
`This report was prepared as an account of work sponsored
`by an agency of the United States Government. Neither the
`United States Government nor any agency thereof, nor any
`of their employees, make any‘warranty, express or implied,
`or assumes any legal
`liability or responsibility for the
`accuracy, completeness, or usefulness of any information,
`apparatus, product, or process disclosed, or represents that
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`herein to any specific commercial product, process, or
`service by trade name,
`trademark, manufacturer, or ‘
`otherwise does not necessarily constitute or imply its
`endorsement, recommendation, or favoring by the United
`States Governmentor any agency thereof. The views and
`opinions of authors expressed herein do not necessarily
`state or reflect those of the United States Government or
`
`any agency thereof.
`
`

`

`DISCLAIMER
`
`Portions of this document may be illegible
`in electronic image products.
`Images are
`produced from the best available original
`document.
`
`

`

`PNNL-13019
`
`Advanced Fingerprint Analysis Project
`
`Fingerprint Constituents
`
`Task Leader: G. M. Mong
`C. E. Petersen
`
`:1‘.R.W. Clauss
`
`September 1999
`
`Prepared for the Assistant Secretary of Defense,
`Office of Special Technology, Technical Support
`Working Group under a Related Services Agreement
`With the US. Department of Energy
`under Contract DE-ACO6-76RLO 1830
`
`Pacific Northwest National Laboratory
`
`Richland, Washington 99352
`
`

`

`SUMMARY
`
`The work described in this report was focused on generating fimdamental data on
`
`fingerprint components which will be used to develop advanced forensic techniques to enhance
`fluorescent detection, and visualization oflatent fingerprints. Chemical components of sweat
`
`. gland secretions are well documented in the medical literature and many chemical techniques are
`
`available to develop latent prints, but there have been no systematic forensic studies of
`
`fingerprint sweat components or ofthe chemical and physical changes these substances undergo
`
`over time.
`
`In this study, seventy-nine samples were collected from very young children, adolescent,
`
`and adult subjects in an effort to gather information which would be representative ofthe general
`
`population. A protocol for this collection was developed which allowed for fingerprint transfers,
`
`aging, and analysis. Only volatile components of fingerprint residue or those which could be
`
`converted to methyl esters through derivatization with diazomethane were studied. The resulting
`
`data indicated that the principle volatile components under 500 daltons are comprised of fatty
`
`acids, stero'id precursors, and wax esters. Aged samples show that squalene, oleic, and-
`
`palmitoleic acid undergo significant degradation afler a 60 day exposure to air, with the total
`
`amount of material extracted decreasing over time, possibly degrading to smaller molecules.
`
`Thus, with aging, various degradation processes serve to shorten and oxidize components in
`
`fingerprint residue possessing unsaturated moieties in their structure. As a result, chemical
`
`functional groups which could possibly be used for fluorescent tagging, are eliminated. A
`
`significant observation was that the inherent inhomogeneity -in_fingerprint samples made
`
`quantitative comparisons (with respect to time) of individual components difficult.
`Considerable variation exists between samples obtained for these aging studies. While most adult
`
`prints yield components indicative of sebaceous secretions, the very young afford mostly
`
`aqueous saline for the print image. Irregular yet interesting results are observed in children
`
`around the age of maturation. A few samples from this age group showed cholesterol as the
`
`ii
`
`
`
`
`
`

`

`major component, far exceeding the concentration of all other components: This phenomenon is
`very fascinating and should be subject to further investigation
`
`In an efi‘ort to gain a better understanding ofthe processes underlying current latent print
`
`development techniques, electron microscopy was used to_study aged samples. Details ofthe
`
`aged fingerprints were developed with silver-based physical developer (PD) solution.
`
`Interpretation ofthe electron micrographs suggests that the PD process may in fact be driven by
`
`electrostatic forces whereby small silver particles provide a "template" that in turn attracts larger
`
`spheres of silver formed in the solution to eventually become the visible silver image ofthe
`
`latent fingerprint. The electron micrographs of developed fingerprint samples are included in
`
`this report.
`
`iii
`
`
`
`

`

`ACKNOWLEDGEMENTS
`
`Several people other than the authors contributed to the successfiil completion ofthe
`
`work described in this report. Robert Ramotowski ofthe United States Secret Service and Mark
`
`Segura ofPacific Northwest National Laboratory provided assistance in assembling a library of
`
`the known fingerprint literature and information concerning the state ofthe art for chemical
`
`development of latent fingerprints. Jim Young at the Environmental Molecular Sciences
`
`Laboratory (EMSL) provided electron microscopy support and micrographs. Jim Campbell,
`
`Scott Clauss, and Karen Wahl all ofthe Pacific Northwest National Laboratory, provided
`
`technical assistance in the completion ofthis report.
`
`
`
`iv
`
`
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`

`

`CONTENTS
`
`SUMMARY ............................
`
`............................................................................................... ..ii
`
`ACKNOWLEDGEMENTS .......................................................................................................iv
`
`1.0 Introduction............................................ .‘. .......................................................................... ..1
`2.0 Sampling Protocol.....................................................................................
`.........................1
`
`3.0 Analysis Protocol ............................................................................................................... ..4
`
`4.0 Analytical Results .................................................................................._. .............................6
`
`5.0 Physical Developer Electron Microscopy .............................................................................9
`
`6.0 Conclusions...................................................................................................................... ..12
`
`7.0 References ....................................................................................................................... ..14
`
`APPENDIX A....................................................................................................................... .. A.1
`APPENDIXB........;.........................................................................................................l...... 13.1
`
`APPENDIX C ................................................................................... ..................................... .. C.1
`
`
`
`

`

`1.0 INTRODUCTION
`
`Successful prosecution ofpeople who commit criminal acts requires strong evidence of
`
`the identity ofthe person or people involved to link them to the crime. Objects connected with
`
`virtually every type of crime, including acts ofterrorism, are routinely examined for latent
`
`fingerprints. Chemical components of sweat gland secretions are well documented in the
`medical literature and many chemical techniques are available to develop latent prints, but there
`
`have been no systematic forensic studies of fingerprint sweat components or ofthe chemical and
`physical changes these substances undergo over time.
`The goals ofthe advanced fingerprint project were divided into several tasks. The first
`task involved assembling a library ofthe known literature pertaining to fingerprint constituents,
`
`analysis of human skin secretions, and information concerning the state ofthe art for chemical '
`
`development of latent fingerprints. This task was completed by a cooperative effort between
`
`Robert Rarnotowski ofthe United States Secret Service and Mark Segura ofPacific Northwest
`
`National Laboratory. The information gathered in this phase Ofthe project was used to explore
`
`the nature and aging characteristics of human fingerprint impressions on a neutral substrate (task
`- 2). The emphasis oftask 2 was to analyze the fatty components ofthe fingerprint in order to
`
`explore what types ofreagents might be developed to visualize the non-aqueous components of a
`
`fingerprint image.
`
`2.0 SAMPLING PROTOCOL
`
`Samples ofhuman fingerprints were collected using an internally approved protocol to
`
`protect the donor’s right to privacy and safety during the collection procedure. The samples
`
`were collected blind, so that no correlation could be made between a person’s print and their
`
`identity. The samples were collected from public sources not affiliated
`
`PNNL, and thus
`
`made re-sampling impractical.
`
`Samples were taken fiom volunteers by having them place their fingertips upon quartered
`pieces ofglass fiber filter paper circles (GFA paper 4.25 cm diameter). So that a normal loading
`
`of human secretions were assured on the sample, a typical grooming motion, such as touching
`
`the face or forehead with the fingers, was encouraged prior to depositing the sample upon the
`
`
`
`
`
`

`

`GFA paper. Prior experiments conducted in the laboratory indicated that the nature ofnormal
`
`fingerprints include a fair amount of sebaceous secretions, -so long as the individual has not
`
`recently washed their hands, and had presumably engaged in touching of other parts ofthe body
`
`which have sebaceous glands. When washed hands were subjected to analysis, the only
`
`components which appeared to be present in the fingerprint samples were water soluble salts.
`
`The touching of the face is such a typical behavioral phenomenon that this was included in order
`
`to create fingerprint transfers which were laden with normal sebaceous secretions. The sampling
`
`protocol included a request that the individual donating prints afirm that they have not applied
`
`cosmetics to the skin within 6 hours of our sampling. This proved to be impractical to enforce,
`
`and often prints from adult females contained a significant amount ofknown cosmetic
`
`components.
`
`The samples were collected by age grouping and sex as the only criteria provided to the
`
`analyst. The arbitrarily assigned age groupings were selected primarily to ascertain the
`
`difference in fingerprint composition, if any, between pre—pubescent children and adults. The
`
`samples collected were grouped as listed in Table 1.
`
`TABLE 1. Categorized list of fingerprint samples.
`
`Age Group
`
`8-12 years
`
`12-15 years
`
`
`
`20-60 years
`
`‘
`
`Total individuals sampled: 79 ,
`
`Samples were requested fiom the volunteers by instructing them to touch 6 sample pieces
`
`of GFA paper with the two major fingers ofthe hand, then to touch the paper again in reverse
`
`order with the same two fingers after a normal grooming motion. In this way, it was hoped that
`
`the samples would be somewhat homogeneous in sebaceous content, while providing a sense of
`security to the volunteer that the multiply touched article would be worthless as. an personal
`
`identifier; the images are smeared, overlaid, and rubbed in the transfer process. The double
`
`touch employed to each sample piece was noted in our estimation oftotal sebaceous loading
`
`
`
`
`
`

`

`upon each sample provided, so that we could make an estimate ofthe amount of component
`material per fingerprint when analysis was completed.
`
`The samples were folded in aluminum foil and a numerical identifier assigned. The
`
`samples were stored in this condition (loosely packed in foil, protected from light), at room
`
`temperature (21 °C), and allowed to age under these conditions up to 60 days. The samples
`taken fi'om adults were analyzed within one day of collection at 10 days, at 30 days, and at 60
`
`days. An observation by Michelle Buchanan's group at the Oak Ridge National Laboratory was
`
`that childrens' samples (those under 12 years) were found to generally have much less sebaceous
`
`secretion than adults [1]; therefore, the protocol was modified to examine these samples at
`
`collection and at 30 days.
`
`
`
`

`

`3.0 ANALYSIS PROTOCOL
`
`When analysis was done, each piece of filter paper was cut in half; and a random set of
`
`three ofthe 12 total pieces were extracted in a serological pipette with 1:1 hexanezchloroform (1
`
`mL) followed by acetone (1 mL) to effect a total transfer of fat soluble components to a SmL
`
`reactivial. The samples were reduced with a' dry stream ofnitrogen over a 40 °C_hotplate. Since
`
`some samples had a tendency to froth, a sliver of silicon carbide boiling chip was added to each
`
`sample. The samples were reduced to about 0.3 microliter, with the residual volume being
`
`primarily hexane/chloroform.
`
`For children’s samples (those under 12 years) we found that the total amount of
`
`sebaceous material was ofien minimal; therefore, one-halfofthe entire sample had to be
`
`consumed in order to obtain analyzable material when the samples involved children.
`
`The free fatty acids and neutral organic compounds collected in this manner were then
`derivatized with diazomethane, converting the fatty acids into the more volatile methyl esters.
`
`We have found diazomethane, prepared from N—methyl-N-nitrosourea, to be a superior method
`
`for generating methyl esters at ambient temperature [2]. Generally the products formed are
`
`nearly free ofundesirable side reactions. The procedure for generation of diazomethane is
`
`outlined below.
`
`Production of diazomethane involves stirring an ethereal slurry ofN—methyl—N—
`nitrosourea (Pfaltz and Bauer Inc., Waterbury, CT) Over an ice cold 40% potassium hydroxide
`
`(KOH) solution. The yellow diazOmethane/ether solution is simply decanted ofi for refi'igerated
`
`storage. In this way, up to 50 mM solutions of diazomethane can be produced, which are
`
`relatively stable for weeks. The methylation is done by dropping the yellow diazOmethane
`
`solution onto the sample until the yellow color persists ( or the evolution of nitrogen ceases). For
`a typical fingerprint sample, only 4—8 drops from a disposable pipette is necessary.
`The samples were allowed to react with diazomethane for about 10 minutes, then the
`
`samples were reduced to near dryness. This procedure allows volatile methyl ethers (traces of
`
`which are present in the ethereal diazomethane solution) to evaporate without loss ofthe heavier
`
`fatty acid methyl esters. This method was tested with samples of octanoic acid methyl ester and
`found to provide 95% recovery ofthe methyl ester, indicating that volatile loss is minimal for C8
`
`acids, and will thus be workable for any methyl ester of C8 chain length or larger. The samples
`
`
`
`

`

`were then transferred to limited volume (100 microliter) gas chromatograph sample vials with a
`
`20 microliter portion of acetone. The known volume oftransfer solvent allowed for an accurate
`
`quantitation ofeach identified component.
`
`'
`
`Gas chromatography / mass spectrometry (GC/MS) was used as the analytical assay for
`the content ofeach sample. The instrument used was a Hewlett Packard 5890 GC coupled with
`
`a Hewlett Packard 5971 Mass Selective Detector (MSD). The mass spectrometer was used in
`
`electron ionization (EI) scan mode, monitoring ions fiom 40-500 daltons, the sampling rate equal.
`
`to 1.3 seconds per scan. The chromatographic conditions used are listed in Table 2.
`
`TABLE 2. Gas' Chromatograph Instrument Conditions
`
`Injector temperature:
`Transfer-line temperature:
`GC temperature program:
`
`Analytical column:
`
`320 °C,
`.
`300 °C,
`initial temperature at 50 °C, hold for two minutes,
`temperature ramp 1 at 15 °C to 150 °C,
`temperature ramp 2 at 8 °C to 280 °C, hold for 2 minutes,
`temperature ramp 3 at 10°C to 340°C, hold at 340°C for 6 minutes.
`Restek® RTX—l crosslinkedpolydimethylsiloxane column.
`0.25 micron x 0.25 mm X 30 m.
`
`Column head pressure:
`
`10 psi helium.
`
`The temperature program provided adequate separation ofthe lighter fatty acid components,
`
`while minimizing the separation time for larger components in the squalene and wax ester region
`
`ofthe chromatogram. A high temperature injector condition and high transfer line temperature
`
`was imperative for obtaining an optimal signal to noise ratio for cholesterol (and presumably for
`
`other steroids); however, the use of a hot injector was found to require fiequent maintenance in
`
`order to ensure proper transfer of cholesterol to the column. Cholesterol is often used as a
`
`GC/MS performance check (as it is a sensitive and difficult analyte); it is fortuitous that it was
`
`also a potential target for this study.
`
`

`

`4.0 ANALYTICAL RESULTS
`
`Markedly different compositions were observed among individuals and between the
`
`heavily sampled 12-15 year age group and adults. The differences were primarily ones of
`
`percent distribution ofthe major components, and not differences in overall chemical species. In
`
`two instances we asked the same volunteers to give samples on different days. The
`
`chromatographic appearance ofthe volatile fatty acids were comparable to that individual’s
`
`initial sample in both cases. Because ofthe observed differences between individuals, it may be
`possible to exclude an individual-as the donor ofa fingerprint based on the chemical composition
`
`ofthe fatty materials in the fingerprint. Ordinarily, adult fingerprints were found to contain (in
`
`order ofabundance) squalene, oleic acid, palmitoleic acid, and palmitic acid. However, there
`
`were donors in which the squalene component was minimal or absent, with the fatty acids
`
`comprising the majority ofthe analyzable material. Table A1 in Appendix A lists the primary
`
`volatile fat soluble materials which were found by GC analysis in an average adult print. Major
`
`components are listed in bold, and these ordinarily make up the bulk ofthe analyzable fatty
`
`materials in a fingerprint.
`For very young children, the samples were nearly devoid offatty acids and squalene; the I
`GO traces are nearly background levels in all samples we collected. It is assumed that the
`
`sebaceous glands are not active in pre-school age children; a larger sampling is necessary to
`'verify the generality ofthis statement. In the case ofchildren (sampling-fiom a 4”“ grade class—
`
`ages 10 to 11 years old) there were three major groupings that were noted for fingerprint
`
`composition. Some in this age group had minimal amounts of fatty acids and squalene, similar
`
`to that observed in the younger subjects. Other volunteers in this age group deposited materials
`which had a fatty acid and squalene composition much like that observed in adults, but in less
`quantity than that observed in samples taken fiom adults. Lastly, 4 samples collected from
`
`female volunteers in this age group, contained a large cholesterol component. The meaning of
`
`this last result is unclear. We could not find a commonly available cosmetic which contained
`
`cholesterol as a major'ingredient. In these particular samples there was no indication of other
`
`common cosmetic ingredients (such as the palmityl wax esters or glyceryl esters common in
`
`hand lotions). It is possible that the secretion of cholesterol is an unreported consequence ofthe
`
`maturation process, at least in some individuals. In our experience, cholesterol was not a major
`
`
`
`
`
`

`

`component in any ofthe adult fingerprints analyzed; the biosynthetic precursor to steroids
`(squalene) wasg usually a pronounced peak in the chromatograms.
`
`Cosmetic ingredients form a signature in some chromatograms, often observed in those
`
`from adult female volunteers. The materials observed include hydrocarbons (tetracosane to
`
`triacontane) from petroleum jelly, short chain glycerides, wax esters (usually palmityl palmitate
`or palmityl stearate), and branched saturated hydrocarbons such as squalane (hydrogenated
`
`squalene). The fimction ofthese latter materials is probably to “moisturize” the skin through
`limiting loss ofwater through evaporation; their constitution is chemically similar to that
`
`observed for native skin secretions. These materials show up as major peaks outside ofthe
`
`normal human secretion pattern. Total ion chromatograms ofaged fingerprint samples from a
`
`representative subject are provided in Appendix C. Figure Cl is a total ion chromatogram ofthe
`initial pattern, showing the abundant squalene at ca. 26.8 minutes, with the fatty acid group
`
`eluting in the 10 -— 21 minute range. The heavier wax esters and sterol components are found
`
`fiom 29 — 35 minutes. When samples were aged, they were re-sampled and re-extracted at 10,
`30, and 60 day intervals (for adult fingerprints).
`‘
`
`A striking problem with our data is the net variability in the subsamples. We chose to _
`
`merely cut the filter paper material in two and randomly mix the 12 pieces. Further, the method
`
`for collection ofthe samples is at the convenience ofthe volunteers, making a homogeneous
`
`print image impractical. Care was taken to
`
`the integrity ofthe fingerprint samples and
`
`their contents by minimizing their exposure to laboratory chemical background and excessive
`
`physical handling; the goal was to allow fingerprints to age in “natural” conditions, as they
`
`would when held as protected evidence. As Figure C.2 demonstrates, the net amount of
`fingerprint material in the l0 day sampling is twice as abundant than in the initial sample; Figure
`
`C.3 fiom the 30 day sample is only 1/10 as much as found in the initial sample. However, Figure
`
`0.4 (60 day sample) depicts about the same level of overall components as observed in the initial
`
`sample. Because ofthis inherent inhomogeneity, comparative quantitation of individual
`
`components over time, is not practical.
`
`Note also that in Figure C.3, squalene is absent, but re-appears in the 60 day sample
`
`(Figure CA), but not at the same relative levels as the day 1 sample (Figure (1.1). It is possible
`that the periphery ofthe print images (light application) are more subject to degradation ofthis
`
`component, or there may be other factors which cause loss or conversion ofthis component
`
`
`
`

`

`(such as microbial degradation). In any case, generalizations can be made from examination of
`
`multiple examples ficom our aging studies and are summarized below:
`
`-
`
`-
`
`°
`
`-
`
`-
`0
`
`Squalene and other multiply-bonded compounds (oleic and palmitoleic acids)
`undergo significant degradation in a 60 day exposure to air, when compared to the
`saturated analogous compounds.
`The abundant wax esters in human secretions also have double bonded moieties
`
`(one series are the palmitoleic esters). These appear to undergo degradation
`somewhat more slowly than oleic acid or squalene.
`'
`The saturated acids and saturated wax esters maintain a more constant relative
`
`relationship over the 60 day aging period.
`Lighter molecular weight saturated acids (especially nonanoic acid) appear in the
`early part ofthe chromatogram ofthe aged samples.
`-
`'
`Traces of diacids (such as nonadioic acid) are found in aged samples.
`The total amount of material found by our derivatization method decreases for
`aged samples, probably thorough degradation to smaller molecules.
`
`The literature indicates that air oxidation ofunsaturated acids such as oleic prefer allylic
`positions. (one carbon away from the double bond), and that subsequent fracture ofthe molecule
`
`would happen in the 8-8 and the 8-11 positions [3]. The observation ofnonanoic acid and
`nonandioic acid in aged fingerprints indicates that the fracturing ofthe oleic acid molecule may
`occur at the site ofthe double bond. This is an important observation, (though it is very
`
`preliminary), in that air oxidation removes a molecular functional group which could be used as
`
`a target for reagent development.
`
`The fate of squalene remains unknown. Squalene initially undergoes addition reactions
`
`which create chromatographic peaks in front ofand afler the squalene peak which show the same
`
`major ions (m/z 69, 81) as squalene. These apparently are transient species which undergo rapid
`
`conversion to other materials; as their concentration never increases to rival the amount of
`
`squalene initially present. In samples in which squalene is abundant, there is a new component
`
`eluting at 22.5 minutes which exhibits ions which may indicate a stable cyclic structure (m/z
`
`209, 314, 349). None of our libraries indicated a good match for this material; not enough was
`
`present in any one sample for further characterization. We believe that this component is a form
`
`resulting from the cyclization of_squa1ene into a steroid precursor [4], however the only basis for
`
`this conclusion is the apparent growth ofthis component in a complex medium where squalene is
`
`declining. Further examination is worthwhile for this component, since if it contains ketone
`
`
`
`

`

`groupings or stabilized double bonds, it would make an attractive chemical target for a
`
`fluorescent tag.
`
`Quantitation ofthe initial fingerprint extracts was accomplished on 9 randomly chosen 8-
`
`12 year old subjects, and 9 adult subjects. Quantitation is estimated as ng per component in a I
`
`single fingerprint impression. Subsampling ofthe entire sample and multiple impressions by the
`
`donor onto the surface have been factored into this estimation. Table A2 in Appendix A details
`
`the major peaks present in the chromatograms for these individuals in descending retention time.
`The material names are abbreviated (so that C14 satis to be read as 14 carbon saturated acid —
`
`myristic acid) and the compounds were estimated by quantitation versus similar compound
`types. We chose as standards stearic acid as a representative for the saturated acid. group, oleic
`acid as a representative ofthe unsaturated acids. Wax esters were estimated as having similar
`
`response to the methyl esters (stearic, oleic) above. Squalene and cholesterol were quantitated
`
`versus the authentic materials.
`
`5.0 PHYSICAL DEVELOPER ELECI'RON MICROSCOPY
`
`In an efiort to‘ ascertain the mechanisms ofthe one available reagent system which
`
`appears to interact with fatty components Of fingerprints, a series ofhigh resolution electron
`
`micrographs were taken ofaged fingerprints which were developed in silver—based physical
`
`developer solution. The formulation ofthe physical developer follows the established procedure
`
`used by the United States Secret Service (provided by Robert Ramotowski) and is detailed
`
`below.
`
`0 Physical Developer (PD) Reagent
`— Deionized water (900 mL)is used to sequentially dissolve the following materials: 30 g
`ferric nitrate, 80 g ferrous ammonium sulfate, and 20 g citric acid.
`— A liter ofwater is used to disperse 4 g n—dodecylamine acetate and 4 mL Synperonic —N
`(nonoxynol—9) to make a detergent solution.
`— Distilled water (100 mL) is used to dissolve 20 g of silver nitrate. A pre-wash solution is
`made by mixing 25 g maleic acid in one liter of water.
`~
`
`Prior to use, the first solution of ferric/ferrous couple (900 mL) is mixed with 40 mL ofthe
`
`detergent solution and 50 mL ofthe silver nitrate solution. Since papers are hardened with
`
`calcium salts, the paper must be rinsed in the maleic acid pre-wash to render the paper surface
`
`neutral to acidic (solubilizing calcium), and may be rinsed once with a bath of deionized water.
`
`
`
`
`
`

`

`- Development
`Using a tray with the PD solution in it, the paper bearing the fingerprint is allowed to
`
`interact with the redox solution and deposit silver to the desired degree ofdevelopment (operator I
`dependent). No studies ofthe 'efl‘ect ofadditional time in the PD developer were conducted. A
`
`few prints from volunteers were selected from the > 60 day aging study and subjected to the PD
`
`development process. Ofthe paper where there was apparent ridge detail (Without smudging)
`
`‘ 1 cm2 samples were given to the electron microscopy laboratory for imaging.
`
`0 Electron Microscopy
`
`The samples were lightly coated with carbon to prevent charging ofthe surface. Electron
`
`micrographs in high resolution/ field emission mode have been examined and stored on the
`
`computer system. Energy dispersive x-ray (EDX) microprobe examination ofthe areas around
`
`the silver particles did not reveal much additional information about the elemental composition
`
`ofthe areas around the silver image; there does not appear to be any measurable concentration of
`
`iron, calcium, or other metals which is acting as a directing influence on the placement ofthe
`
`silver particles in the image. So far, we can only say that there is a collection of larger particles
`
`of silver (ca. 7 micron diameter) in the area ofthe print image than in areas without the print
`
`image. An underlying structure of extremely small silver particles (ca. 100 nm or smaller)
`
`appear to be more concentrated in the areas ofthe print. The morphology ofthe larger particles
`
`indicate that they possess much surface area (and are formed firom collected silver crystals fiom
`
`the solution) and the overall spherical nature ofthe 7 micron silver particles supports the notion
`
`that these are formed in suspension in the solution. These larger particles are selectively
`deposited on the paper surface so that a larger net number ofthese particles make up the visible
`
`image ofthe developed latent fingerprint. There does not appear to be a direct mechanism which
`
`attracts silver to fatty residues on the paper; however, there are particles which show apparently
`
`fluid bridges between the silver particles and the surface ofthe paper in the areas which show
`ridge detail. More commonly, the larger particles are just more concentrated in the areas of
`
`visible ridge detail.
`
`An experiment was independently conducted by Jim Young (EMSL) on the areas ofthe
`
`samples which contain fingerprint ridge detail. Mr. Young looked for the K—alpha backseatter X-
`
`ray for silver as a sensitive probe for the overall diffuse concentration of silver in the cellulose
`
`
`
`10
`
`
`
`

`

`matrix. The test was to ascertain ifthere exists a larger component ofnanometer sized particles
`
`of silver in the areas ofthe fingerprint image.- Electron micrograms ofa fingerprint sample are
`. shown in Appendix B. Figure B] depicts X-ray backseatter images which indicate that there is
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`indeed a large concentration of extremely small silver particles (below the resolution limit ofthe
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`EM system) concentrated in the area ofthe fingerprint ridge. The concentration ofthese small
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`particles is generally less in the areas which do not exhibit ridge detail. Though these images are
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`less spectacular than those which show the large particle morphology ofthe silver imaged
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`fingerprint (Figure B2), the interpretation ofthese electron micrographs is believed to be very
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`important. Drawing fiom the multimetal deposition process [5], the PD process may in fact be
`driven by electrostatic forces associated with the deposition ofsilver particles ofnanometer size.
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`These extremely small particles then provide a “template” to attract larger spheres of silver
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`formed in the solution (by electrostatic imbalances) to form the visible silver image ofthe latent
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`fingerprint. Further work in this area is warranted to develop a theory ofthe PD process.
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`11
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`

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`' 6.0 CONCLUSIONS
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`The data collected show that the principle volatile fatty components (up to molecular
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`weight 500) of a fingerprint image consist of fatty acids, steroid precursors (as squalene), and
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`wax esters. Upon aging, various degradation processes serve to shorten and oxidize those
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`components with unsaturated moieties in the molecule. This circumstance removes a principle
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`chemical functional group, which could be used as a chemical “handle” to attach a fluorescent
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`tag to the fingerprint image.
`The fingerprint image apparently becomes hardened and less susceptible to partitioning
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`of coloring agents through a number ofprocesses. The first process which contributes to the
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`hardening of the print is due to loss of moisture. Initial experiments were performed on glass
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`slides which indicated loss of up to 85% of the fingerprint’s weight (presumably as water) over a
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`two week timeframe. The consolidation of the materials in the fingerprint to a waxy layer
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`decreases the surface area for contact with reagents which might be used to partition with the
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`fingerprint image (cf. the inability ofNile Red to partition into aged prints).
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`Secondarily, there are chemical changes that serve to consolidate the saturated fatty acids
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`as the major components ofthe fingerprint image while air oxidation products ofthe unsanirated
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`components form The air oxidation products and saturates tend to have a more orderly crystal
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`structure than the unsaturates, leading to a harder, more crystalline surface in the