Chemical Dating Techniques for
`Latent Fingerprints: A Preliminary Report
`
`by
`Robert D. Olsen, Sr.
`Criminalist 111
`Kansas Bureau of Investigation
`1620 Tyler
`Topeka, KS 66612-1837
`
`This i.~ an abridged te.~t of a paper presented at the 71.vt Annual
`Educational Conference of the International Association fbr [(ien[~ji-
`(ation, I.ondon Tara Hotel, Kensington, on 29 August 1986.
`
`There is no scientific method for dating latent finger-
`prints and nothing in this paper should be construed as a
`viable dating technique. The purpose of this paper is
` am presently
`merely to acquaint you with research
`conducting in the hope of developing such a technique
`and, by so doing, to encourage others to perform research
`I
`in this area.
`To explain the premises underlying my research project
`in attempting to chemically date latent fingerprints, it is
`necessary to first present the sequence of events and
`observations that led me to research in this area.
`
`BACKGROUND
`
`In a previous paper [1], I gave a brief description of the
`naturally occurring fats and oils found in latent print
`residue, a class of substances known as lipids. That paper
`was a continuation of a previous paper on the chemical
` sweat [2], and the purpose of both
`composition of
`was to encourage research for new and improved latent
`fingerprint techniques. I had hoped the material would
`palmar
`provide someone with a research idea.
`I have been interested in the lipid material found in
`latent print residue as my view was, and remains, that it is
`a topic largely neglected by researchers in the fingerprint
`field. Texts and articles on latent fingerprints mention the
`lipid material only very generally as products of
`sebaceous origin and make no attempt to adequately
`describe the exact composition.
`A 1974 report [3] shows the diversity and complexity of
`lipid material on human skin surfaces. Of particular
`interest in the report cited are tables 1 and 2, which show
`the percentage of each lipid component type in relation to
`the total amount of lipid material and give a break-down
`of the unesterified fatty acids. These fatty acids are not
`found in the sebaceous glands; they form on the skin
`surface by hydrolysis. Of the 21 fatty acids listed in table 2
`of the cited reference, 14 are unsaturated.
`It is my view that certain latent fingerprint techniques,
`such as iodine fuming, are dependent upon the double
`bonds of the unsaturated fatty acids, and that the iodine is
`absorbed by the fatty acids by the process of
`
`4-
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`IDENTIFICATION NEWS
`
`- FEBRUARY, 1987
`
`halo-
`
`genation. in addition to the free fatty acids, the un-
`saturated fatty acids are also in the triglycerides and wax
`esters present. Although not specifically mentioned in my
`first article, the double bonds of
` also play a role
`in the iodine reaction. There are those who disagree with
`this view and who hold that the reaction is with water [4],
`squalene
`or that the iodine addition to double bonds is colorless
`and the color of iodine-developed prints is simply due to
`absorption by the latent print residue [5].
`The use of iodine fuming to visualize unsaturated
`compounds by reaction with the double bonds is too well
`established in scientific literature [6-9] as an accepted
`technique for visualizing such compounds to warrant
`further debate here. insofar as latent print development,
`the issue is immaterial. Our concern is whether the ridge
`details match those of a particular inked impression and
`not the chemical processes involved. The visualization of
`unsaturated lipids is important, from my viewpoint, in
`that it led to the premise that these lipids may hold the key
`for a dating technique for latent prints on nonporous
`surfaces.
`To determine whether the iodine was reacting with the
`lipids or water in latent print residue, a latent print was
`deposited on a silica gel coated glass plate and the plate
` C for
` minutes to
`was placed in a desiccator at
`remove its water content. The plate was then subjected to
`iodine fumes and the resulting visualized print was
`100°
`30
`photographed.
`The iodine-developed print was then cleared with
`ammonia fumes and the plate treated with osmium
`tetroxide fumes. Osmium tetroxide is well known for its
`reaction with the double bonds of unsaturated com-
`pounds. The osmium tetroxide-developed print was photo-
`graphed and compared to the photograph of the
`developed print. In intensity, shading, strength and
`clarity, both prints had about the same appearance.
`iodine-
`Undeniably water and other substances in latent print
`residue in which iodine is soluble or absorbed are
` believe
`important in the development of the print, but
`this test illustrates the major role of lipids in that
`development.
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`To further establish the role of lipids in the reaction
`between iodine and latent prints, test fingerprints on a
`glass plate were removed with petroleum ether and
`spotted on separate silica gel coated 2.5 x 10 cm glass
`thin-layer chromatography (TLC) plates. The lipids were
`resolved by using a solvent series of successive develop-
`ment in hexane (to 9 cm), benzene (to 9 cm), and finally a
`mixture of hexane:ether:acetic acid 70:30:1 (to 4cm) [10].
`The resolved lipids on the first plate were then charred
`by spraying with 50-percent sulphuric acid and heating
`the plate to 220” C. A second plate was then visualized
`with iodine fuming. To preclude the possibility that the
`iodine was also being absorbed by saturated lipids, the
`plates were also sprayed with a l-percent solution of
`a-cyclodextrin in 30-percent ethanol, dried, placed in a
`humidity cabinet for one hour at room temperature, and
`then subjected to iodine fumes [18]. The resulting chro-
`matograms did not differ significantly from those
`exposed only to iodine fumes. Although this procedure
`establishes that the iodine is reacting with unsaturated
`compounds, it does not identify them.
`A chromatogram was then prepared to compare the
`extract from latent print residue with known standards of
`lipids using the same solvent series. The resulting
`chromatogram was visualized with iodine fumes. This test
`leaves little doubt regarding the types of lipids in latent
`print residue reacting with iodine. The first column is an
`extract from latent prints deposited on glass; 2, squalene;
`3, cholesterol oleate (wax ester); 4, triolein (triglyceride);
`5, cholesterol; and, 6, oleic acid (unsaturated fatty acid).
`Numerous chromatograms were made and I noted that
`differences could be found in the visualization of extracts
`from fresh prints and those from prints that had been set
`aside for several weeks. It appeared that the free fatty
`acids, cholesterol and squalene were not present in the
`older prints.
`To simulate aging and test this observation, latent
`prints were deposited on glass plates and placed in an
`oven at 90° C for periods ranging from 30 minutes to 4
`hours. The latent residue was then extracted and a thin-
`layer chromatogram made using the same solvent series
`as previously mentioned. It was found that the lipids
`disappeared in the following sequence: free fatty acids,
`cholesterol, and squalene. This is possibly due to
`molecular weight, which is generally inversely propor-
`tional to vapor pressure. The triglycerides and wax esters
`continued to be present in all the samples tested.
`
`ANALYTICAL TECHNIQUE
`
`Thin-layer chromatography is not, however, the most
`suitable analytical technique for continuing research in
`this area. To obtain sufficient lipid material for making
`the chromatograms thus far cited, numerous prints had to
`be deposited on each glass plate used for collecting the
`prints. Regardless of the results that may be obtained, no
`dating technique would be practical unless a single latent
`print could be analyzed. The initial problem is, then, the
`development of an adequate analytical technique even
`
`before studying the kinetics of the individual lipids.
`Such techniques do exist. During the war in Vietnam,
`one problem encountered was the flow of men and
`materials down the Ho Chi Minh Trail in Laos and
`Cambodia. The trail could be bombed and strafed with
`aircraft, but this was ineffective unless the enemy was
`actually on the trail at the location pinpointed. The
`United States Army conducted considerable research to
`develop an apparatus that could detect enemy troops on
`the trail.
`Sound and motion detectors were not practical as
`animals and weather could both give false alarms. What
`was needed was a remote detection apparatus that would
`unfailingly detect only human beings. Taking a cue from
`an existing bio-sensory device (bloodhounds), which has
`shown a remarkable ability to detect human beings by the
`chemical signature of their spoors, extensive resarch was
`directed towards detecting human beings by their body
`odors, or smell.
`All types of natural human exudates were examined as
`well as methods for detecting them in their vaporous
`form. All of the research was initially classified security
`information, but some of it has been declassified in the
`last ten years [11- 16]. Much of the analytical instrumental
`techniques has been outdated, but this material provides a
`start for developing an analytical technique for examin-
`ing the residue of a single latent fingerprint. It almost
`seems unnecessary to point out that there is abundantly
`more material available for analysis in the residue of a
`latent print than can be found in odors.
`Studying the Department of Defense research available
`and correlating it to my proposed research, it appears that
`the best analytical technique will be either gas chro-
`matography or high pressure liquid chromatography. A
`sample of latent print residue was run on a Hewlett-
`Packard 5992V Gas Chromatograph/ Mass Spectrome-
`ter. Squalene, cholesterol, behenic acid, lauric acid,
`myristic acid, palmitic acid and stearic acid were identi-
`fied at this time, but not the heavier wax esters and
`triglycerides as high temperature columns were needed.
`Since then the KBI has purchased a Hewlett-Packard
`5890 Gas Chromatograph with 5970B Series Mass
`Selective Detector and software. An initial preliminary
`analysis of latent print residue for lipids was run on this
`instrument, but again we need a high temperature column
`for satisfactory results.
`The research is presently at a standstill until we obtain
`the high temperature columns. I believe that within the
`next year or two we may be able to form a conclusion as to
`whether or not it may be possible to develop a dating
`technique for latent fingerprints on nonporous surfaces.
`If such a techniuqe is possible, many factors will have to
`be taken into consideration and properly noted at the
`time the prints are collected as both temperature and
`humidity will both have an influence on the presence or
`absence of the lipids.
`I must also stress that we are an operational crime
`laboratory and our priority is case work. All our research
`
`(“on(inuc~! on page 12
`
`FEBRUARY, 1987- IDENTIFICATION NEWS -5
`
`2
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`

`

`Chemical Dating Techniques...
`
`( 011// 111(1’(/ //(1/)1 /J(ll.’(’ 5
`
`must be on a time and equipment available basis. If any of
`you find this line of inquiry of interest, please feel free to
`conduct your own research and you can depend upon us
`for all the assistance we can provide.
`
`ADDENDIJM
`
`Subsequent to the presentation of this paper, the
`author has learned of research in dating latent prints
`using high performance liquid chromatography (H PI.C)
`by a team in Calcutta, India. Anyone interested in this
`area of research should also read “Aging Studies on
`Fingerprint Residues [Jsing Thin-Layer and High Per-
`formance Liquid Chromatography”, by Y. S. Dikshitulu,
`Lala Prasad, J.N. Pal and C. V.N. Rae, Forensic Science
`International, volume 3 I ( 1986), pages 261-266.
`
`NOTE
`
`The illustrations that accompanied the original paper
`have been deleted from this article as it is the author’s view
`that they will not reproduce well in the printed media. If,
`however, anyone wishes a copy of the illustrations. they
`may contact the author.
`
`REFERENCES
`Olsen, R. D., “The oils of latent fingerprints”, The Finger-
`print and Identification Magazine, vol. 56, no. 7 (January
`1975), pp. 3-12.
`
`, “The chemical composition of
`palmar sweat”, The Fingerprint and Identification Maga-
`zine, vol. 53, no. 10 (April 1972), pp. 3-23.
`Nicolaides, N., “Skin lipids: their biological uniqueness”,
`Science, vol. 186 ( 1974), pp. 19-26.
`Almog, J., et. al., “Chemical reagents for the development
`of latent fingerprints. 11: Controlled addition of water vapor
`to iodine fumes - a solution to the aging problem,” Journal
`of Forensic Sciences, vol. 24 ( 1979), pp. 43 I-436.
`Goode, G. C., and J. R. Morris, I.atent Fingerprints: A
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`Detection in Scene-of-Crime Examination. AWRE Report
`No. O 5/81, Aldermaston, Berks., Great Britain, July
`1981, p. 36.
`Stahl, E. (editor), Thin-Layer Chromatography. Springer-
`Vet-lag, New York, 1969. p. 147.
`
`1.
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`6.
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`The Identification News
`Walter M. Thomas
`Editor - IAI
`P.O. Box 3054- Kinston, NC 28501
`919-522-3698: Home/Nite Calls
`919-522-2911: Office/Day Calls
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`12-
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`IDENTIFICATION NEWS
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`- FEBRUARY, 1987
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`Koch, R. B., Biochemical Studies on the Initiation of Odor
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`
`/
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`Ashley R. Crooker, Jr.
`Secretary- Treasurer
`International Association for Identification
`2516 Otis Dr.
`Alameda, CA 94501-6370
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