`from adults and children
`Michelle V. Buchanaif, Keiji Asanoa, and Arthur BOhanOflb
`Chemical and Analytical Sciences Division, Oak Ridge National Laboratory,
`P.O. Box 2008, Bldg. 5510, Oak Ridge, TN 3783 1-6365
`boxville Police Department, 800 Church Ave., Knoxville, TN 37915
`
`ABSTRACf
`Theobservation that d fingerprinis ofchildrendisappear from surfaces more quickly than those of adults initiated a study to characterize
`d chemicalcomponents in fingerprints. Samples were obtained from about 50 indiViduals ranging in age from three to 64 by extracting
`chemicals from the finps using rubbing a]coIxL Using combined gas chromatography/mass spectrometry, a wide range of compounds
`were identiñed. It was found that the chemical compositions of fingerprints were cijiite different in children and adults. In general, the
`samples obtained from children contained higher levels ofrelalively volatile free fatty acids. Samples from adults were found to have higher
`concentrations ofless volatile long chain esters of fatty acids. These esters are thought to originate from sebaceous glands located on the
`face and the levels ofthese compounds increase substantially after puberty. In addition to these compounds, a variety of other compounds
`were observed that could be used to develop improved methods for fingerprint detection at a crime scene. Further, the observation of
`specific compounds raises the possibility of being able to identify personal traits (gender, habits, diseases, etc.) via the analysis of
`components in fingerprints and/or skin.
`Keywords: fingerprints, chemical analysis, gas chromatography/mass spectrometry
`1. INTRODUCTION
`In July 1993, a three-year-old gui was abdixted aixi brutally murdered in Knoxville, TN. The suspect initially confessed, but later recanted
`his confession. This made it imperative that evidence linking the child to the suspect be found. Despite witnesses placing the child in the
`suspect's vehicle, a thomugh eximinition of the vehicle did not yield any fingerprints from the child; only the suspect's fingerprints were
`found. This same phenomeixm was observed previously in a child kidnaping where the vehicle could not be examined for prints until four
`days after the crime.
`This raised d possibility that the fingerprints from children did not last as long on surfaces as fingerprints from adults. After contacting
`fingerprint experts from several agencies in this country and abroad, ix information about the disappearance of children's fingerprints from
`surfaces could be found. To test out this possibility, a simple experiment was conducted. In August 1993, children were asked to deposit
`finger on the inside of a number of vehicles. Within 24 hours, no fingerprints could be found. As a follow-up, a group of children
`and adults were asked to touch the outside surfaces of new, clean plastic and glass soda bottles, which were placed in cases. Half of the
`cases were stored in a basement at relatively constant temperawre and humidity levels. The other half were placed in the back of an
`automobile, which was subjected to a range of temperatures, including summer temperatures of greater than 85°F. Samples were tested
`by conventional dusting over a several day period. It was discovered that the children's fingerprints disappeared within 24 hours, while
`d prints from adults lasted at least several days. Further, the fingerprints from bottles in the basement lasted much longer than the ones
`in the cars. These samples were collected every 30 days for the entire year of 1994 and similar results were observed each time. The only
`difference observed was that the children's fingerprints disappeared faster at higher temperatures.
`
`Further author information:
`M.V.B. (Correspondence): Email: buchananmv@ornl.gov, Telephone 423-574-4868; FAX 423-576-8559
`KA.: asanokgoml.gov Telephone 423-574-7469; FAX 423-576-8559
`A.B.: Telephone 423-521-1209; FAX 423-521-1205
`
`SPIEVol. 2941 • O-8194-2343-2/97/$1O.OO
`
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`The relationship between the disappearance of the fingerprintsand temperature suggested that there was a difference in the chemical
`composition of fingerprints between adults and children. Literature searches showed very little information on the chemical composition
`of fingerprints and nothing on the fingerprints of chi1dren A study was therefore initiated to analyze the components in the fingerprints
`of children and adults to ascertain if an explanation for the faster disappearance of children's fingerprints could be obtained.
`2. EXPERIMENTAL
`
`2.1 Sample preparation
`Volunteers ranghig in age from three to 64 were asked to suhnit samples. The sampling protocols were reviewed and approved by the Oak
`Ridge National Laboratory/Oak Ridge Associated Universities (ORNL/ORAU) COmmittee for Human Studies prior to initiating this study.
`Approximately 1 mL of rubbing alcohol (70% isopropanol in water) was pbced in a small (4 mL) sample vial sealed with a Teflon-lined
`screw closure. The vials sere cleaned prior to use by sonicating in acetone for 10 minutes and dried at 100°C for a minimum of onehour.
`In
`To obtain a sample, the subject placed a fingertip on top of the vial and shook the rubbing alcohol against the fingertip for one minute.
`some instances, the subject was asked to wipe the tips of the fingers across his/her forehead prior to shaking the sample vial against the
`fingertip. The vials were labeled by a code number to protect the identity of the subject. Prior to analysis, the samples were concentrated
`under a small stream of argon gas until approximately 50to 100 L of solution remained. Some samples were analyzed directly at this
`stage. Others were derivatized using a methylating reagent to allow polar compounds to be analyzed more readily. In this case, lOOjiL
`ofMethyl-8® reagent (Pierce Omical Comwiy, Rockford, IL) was added to the concentrated sample solution. The vial was then heated
`for 20 minutes at 60°C and the sample was then ready for analysis.
`2.2 Sample Analysis
`The samples were anal on a combincd gas chromatograph/mass spectrometer consisting of a Varian 3400 gas chromatograph interfaced
`to a Finnigan rrS4O quadrupole ion trap mass spectrometer. A fused silica capillary column, 30 m in length and 0.25 mm ID with a bonded
`(5%-enyl)methylpolysiIoxanc stationaiy ase (DB-5, J&W Sciendflc, Folsum, CA) was used to separate the components prior to analysis
`in d mass spectrometer. Helium was used as the carrier gas at a head pressure of 5psi. The injector temperature was held at 280°C and
`the column oven was temperature programmed, starting at 100°C for one minute and ramping at 5°C/rain to 280°C, where the column
`was held up to 30 minutes. The mass spectrometer transfer line was maintained at 280°C and the manifold heater for the analyzer cell was
`maintained at 220°C. AU mass spectra were obtained using electron ionization (70 eV). In some cases, chemical ionization spectra were
`obtained using isobutane or methane as a reagent gas to verify molecular weights of the observed compounds. In this case a Hewlett-
`Packard 5985 GC/MS, equipped with a similar chromatographic column and operated under similar chromatographic conditions, was
`employed. The reagent gas was introduced into the ion source at approximately 0.5torrand the chemical ionization plasma was formed
`using 200 eV electrons.
`
`3. RESULTS AND DISCUSSION
`During the course of these studies, nearly fifty subjects were studied, with about half rangüig in age from three to 13 years and the other
`half, from 15 to 64 years. The chromatographic profiles obtained from the samples clearly fell into two classes, one made up of
`prepubescent children and the other from adults. The total ion chromatogram shown in Figure 1 is taken from a four year old boy and is
`typical of the profiles obtained from children. The early eluting peaks are composed primarily from long chain carboxylic acids having
`from twelve (Ca) to more than twenty-six (C,J carbons, including palmitic and stearic acids. Because the samples were methylated, these
`compotuxis were detected as methyl esters of the acids. These compounds clearly are the major components in the samples obtained from
`children. Figure 2 is a total ion chromatogram obtained from an adult male (age 27). This chromatogram is quite distinct from the one
`in Figure 1 and is qtüte typical of those obtained from adults. In this profile, long chain carboxylic acids are also observed, but at amuch
`lower level than in the samples from children. However, a number of higher molecular weight compounds are also observed at retention
`times greater than 50 minutes. These compounds, which are not observed in the child's profile in Figure 1, are long chain alkyl esters of
`carboxylic acids, such as C16 esters of C8 acids. General structures of the long chain carboxylic acids and esters are given in Figure 3.
`
`Samples taken after the subject had wiped his/her forehead revealed even larger amounts of the long chain alkyl esters. These esters are
`members ofa class ofcompoimds called lipids. Most of the lipids on skin are thought to originate from sebaceous glands' and the highest
`density of these glands occur on the scalp and face, with none on the palms. Because an individual frequently touches his face and hair,
`it j5 logical that this material is transferred to U fingertips and can be found in fingerprints. Further, in adults, it is thought that over95%
`ofthe skin surface lipids arise from sebaceous excretions.2 The surface lipids in children, on the other hand, are thought to arise from the
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`epidermis and are present at far lower levels than adults, with sebaceousexcretions increasing only afterpuberty. This difference in the
`content of these lipids may account for the observed differences in the disappearance of latent fingerprints from surfaces. At elevated
`temperatures, d bwer molecular weight, volatile carboxylic acids that are prevalent in young children would tend to evaporate from the
`surface. With only low levels of the higher molecular weight, less volatile long chain esters, it is quite likely that little material would
`remain from a child's fingerprint to allow the print to be observed using conventional dusting techniques. Conversely, the higher levels
`ofthe alkyl esters found in adult fingerprints would remain on the surface longer, allowing fingerprints to be observed over longer periods
`of time.
`Squalei (see Figure 3) was by far the most abundam compound identified in the extracts, even though the solubility of this compound in
`alcohol is relatively low. This compound is an intermediate in the biosynthesis of cholesterol3 and is seen at a retention time of
`approximately 38 minutes in d chromatograms shown in Figures 1 and 2. Note that the levels of squalene are typically lower in children
`than adults, which again is probably a reflection of the fact that this compound originates primarily from sebaceous glands.2 Cholesterol
`was observed in all samples studied and may be seen at a retention time of approximately 45minutes in the cbromatograms in Figures 1
`and 2. This compotmd is thought to arise primarily from the epidermis and is typically observed at much higher levels in children than
`in adults. The chromatogram in Figure 2 was from an adult that had unusually high response for cholesterol compared with the other adults
`tested. For the other adult samples, the cholesterol peak was present, but in much lower quaEtities than a related compound, cholesteryl
`acetate. Many structural isomers of this compound exist, and one is shown in Figure 3. This compound can be observed in the
`chromatographic profile shown in Figure 1, which is the sample obtained from the child. The levels of cholesterol and cholesterol acetate
`isomers s;ere observed to change beten different individuals. This again may be observed in Figure 2, where this adult male had a large
`cholesterol peak and little cholesteryl acetate.
`Other compounds were also identified in the samples taken from the fingertip extracts. Samples taken from the fingertips of smokers
`contained traces of nicotine. This compound may have originated from handling tobacco products or from exposure to tobacco smoke,
`rather than from excretion oftl coinpoimd from fr skin. However, during frse studies nicotine was also identified in the fingertip extract
`ofan adult who had quit smoking cigarettes two weeks prior to the experiment, but was chewing nicotine gum. In a few samples, traces
`ofsteroids ;ere also observed in fingertip extracts. The presence of steroid hormones and their metabolites has been reported in human
`skin and has been related to gender and different physiological conditions, including diet, cancer, and others.
`The results ofthis study have shown that there is indeed a difference in the composition of materials presem in the fingerprints of children
`and adults. The lower levels of higher molecular weight, less volatile materials in children's fingerprints could explain the disappearance
`offingerprints from crime scenes. As a result, for any crime involving a child, it is imperative that fingerprints be examined as soon as
`possible. A systematic study of the rate of disappearance of specific fingerprint components as a function of temperatere and other
`environmental parameters is planned to assess which compounds are retained on surfaces. These studies will be used to identify specific
`compoints found in tl fingerprints ofboth children and adults that could be used for the development of an optical detection method that
`would allow fingerprints to be detected more reliably.
`1 general chemical characterizaiion ofcomponents in fingerprints our laboratory is continuing. In these initial studies, rubbing alcohol
`was used to extract components directly from d fingertips. This permitted more material to be collected for analysis than simply extracting
`individual prints off a non-porous surface. Rubbing alcohol was chosen as a solvent in this study due to its relatively low toxicity.
`However, it should be noted that this solvent will not extract all the compounds present on the surface of fingertips, and the compounds
`found in this study are primarily those that have appreciable solubility in this solvent. Other solvents and/or sampling methods are being
`investigated to allow a wider variety of components to be identified as part of these studies.
`In aixtber area ofresearch, we are investigating potential uses of the chemical composition of fingerprints in forensic, clinical, and other
`applicadons. The fact that the types and quantities of some compounds change from person to person opens the possibility that one might
`be able to analyze components in fingerprints and/or extracts taken from fingertips and obtain information about the individual. For
`example, by analysis of fingerprints, narrowing down the list of potential suspects may be possible based on the presence or absence of
`targeted components, such as hormones, nicotine, illegal drugs, and others. Excretion of amphetamines in human sweat has been
`documented.4 Thus, the potential exists for non-invasively collecting samples and detecting drugs and/or drug metabolites in materials
`obtained from fingerprints and/or skin. This would eliminate the need to collect and handle potentially hazardous biological samples, such
`as blood and urine. Further, with development of sensitive analytical schemes based on mass spectrometry, optical, or other methods,
`screening individuals rapidly for the presence of illegal drugs may be possible, rather than sending the samples to a remote laboratory for
`analysis and waiting days or even weeks for results. For example, we have shown the ability to detect trace levels of drugs in microliter
`quantities of milk using quadrupole ion trap mass spectrometry.5 This technique minimizes the need for sample preparation and can be
`completed in a few minutes rather than four or more hours by conventional gas chromatography/mass spectrometry. The ability to detect
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`targeted components rapidly in fingerprints and/or skin would bave broad application in forensic investigations,
`and clinical applications.
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`law enforcement activities,
`
`ACKNOWLEDGMENTS
`Supportfor this researchwas providedby the Laboratory Director's Research and Development program at Oak RidgeNational
`Laboratory (ORNL) and the Department of Energy Office of Energy Intelligence. Oak Ridge National Laboratory is managed for the
`United States Department of Energy by Lockheed Marün Energy Research Corporation under contract DE-ACO5-96OR2244. The
`authors would like to acknowledge Jennifer Fletcher (Auburn University), C. Scott Schultz (Transylvania University), Matthew
`Johnson (North Dakota State University), and Steve Jarboe (Transylvania University), who were major contributors to this research
`during undergradnate research projects conducted in our laboratory. Special thanks is also given to Dr. Alvin Trivelpiece and Dr.
`Bruce Jacobsen of ORNL for assistance in this project and to Dr. Antonio Cantu and Mr. RObert Ramotowsky of the U.S. Secret
`Service for helpful advice.
`
`REFERENCES
`N. Nicolaides, "Skin Lipith their Biochemical Uniqueness", Sdence,186, pp. 19-26, 1974.
`E.L. Rongone, "Skin Structure, Function and Biochemistry", inDermatotoxicology, ed., F.N. Marxulli and H.I. Maibach,
`pp. 1-70, Hemisphere Publishing, Washington, 1983.
`A.L. Lehninger, Biochenzistiy,2nded., p. 280, Worth Publications, Inc. New York, 1975.
`T.B. Vree, A. Th. J. M. Muskens, and J. M. Van Rossiun, "Excretion of Amphetamines in Human Sweat", Arch. mt.
`Pharmacodyn, 199, pp. 311-317, 1972.
`S.A. Barshick and M.V. Buchanan, "Rapid Analysis of Animal Drug Residues by Microcolumn Solid-Phase Extraction and
`Thermal Desorption-Ion Trap Mass Spectrometry", J. Assoc. Offic. Anal. Chem. Intl., 77, pp. 1428-1434, 1994.
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`Figure 1 . Total ion chromatographic profile of fingertip extract from four year old male. Peaks at
`approximately 38, 45 and 47 minutes are squalene, cholesterol, and an isomer of cholesteryl acetate,
`respectively.
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`Figure 2. Total ion chromatographic profile of fingertip extract from adult male. Peaks at approximately 38
`and 45 minutes are squalene and cholesterol, respectively.
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`Cholesterol
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`Cholesteryl Acetate Isomer
`
`Squalene
`
`...
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`Typical carboxylic acid with varying carbon backbone length
`
`. .
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`Typical long chain ester with varying carbon backbone length
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`Figure 3. Structures of compounds identified in fingertip extracts.
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