Reactive Surfaces Ltd. LLP
`Ex. 1038 (Ray Attachment C)
`Reactive Surfaces Ltd. LLP v. Toyota Motor Corp.
`IPR2016-01914
`
`

`

`sum—rs
`
`Fingerprint Mechanics
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`
`
`Pufliflaed and ijtributed Thmugimul' Hm fi'mid by
`
`CHARLES C TI-IDMAE ' PUBLISHER
`
`Bannerstnne- Hmm:
`
`301427 Ens-t [mu-emit: Avenue. Springfield. Illinnis. 1.7-5-5.
`
`it
`This. hm]: 1'3 pmtected by cum'fight. Ha part III
`may he reprflducfid in any manner will-mu: “Till-Ell.
`permjliiun fmm the publisher.
`
`E13115, byCI-LJLEIEE C 'I'I'I'DI'LIAE - PUBLISHER
`HEN fllfififllTlfl-E [:Inlhi
`ISBN flvIfiSvflEIflfl-I {pip-III
`Lib-Ian: [If Cnngefi CataIflg Card Humber: 77-12935
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`afl Janis Hf
`H'flh THGJIAS SEEKS carafuf aflrnfinn 1": giren tn-
`manufacturing and dgfign. It E; the PuIJIr'sher's desire :9 mm Imh that are
`.mmisfudnry as In their piawimf qualms: and artistic panibih'flgs
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`law: {If qunfity that JEWFE' a gmd nmne and guild will
`
`Library Inf flanges: Catalnging in Publicatiun Data
`
`Scan. "Walter E.
`
`Scat-F5 Fingerprint mechanics.
`
`Biinngrnphy: 1;.
`Includes. index.
`
`1. Fingerprints. I. 015211, Hubert D- II. Title-
`III. Title: Fingerprint mechanic-s-
`HFEflT-IIEEII 1977
`334.125
`
`77-12955-
`
`EENU—JW—flfiflfl-l — ISBN fl-JQ'S-flfiiflflfi lJII’flM
`
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`w
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`108
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`Scott’s Fingerprint Mechanics
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`Richardson, L., and L. Kade: “Readable fingerprints from mummified or
`putrefied specimens,” Identification News. vol. 23 (Jan, 1973), p. 3.
`Scott, C. C.: Photographic Evidence. St. Paul, MN, West Publishing (30.,
`1955, vol. 2, p. 216.
`“Shark and sea victim identified by fingerprints,” FBI Law Enforcement Bul-
`letin. vol. 19 (Aug., 1950), p. 21.
`Simon, A., and H. Jordan: “Die daktyloskopie von brandleichen mit sili-
`kongummipaste,” Archie fur Kriminologie. vol. 141 (1968), p. 28.
`Sullivan, T. F.: “Entire hand skin peels off like a glove: Victim named,”
`Fingerprint and Identification Magazine. vol. 52 (Dec, 1970), p. 12.
`Thomson, M. W.: “The fingerprinting of cadavers,” Fingerprint and Identi-
`fication Magazine. vol. 53 (Aug, 1971), p. 14.
`“3,500—year old fingerprints,” Science Digest. vol. 31 (Jan, 1952), p. 60.
`Trotter, C. L.: “Organized plans needed to identify disaster victims,” FBI
`Law Enforcement Bulletin. vol. 29 (May, 1960), p. 13.
`Truby, C. L.: “Advice on recording fingerprints that are difficult to ink and
`record,” Military Police Journal. vol. 12 (June, 1962), p. 12.
`“Ways of obtaining good fingerprints, insuring legibility,” FBI Law Enforce-
`Wier, B. R: “How liquid latex identified Willie Williams,” Fingerprint and
`Identication Magazine. vol. 40 (Nov., 1958), p. 3.
`Wilson, R.: “Fingerprint
`identification of a burned body,” Identification
`News. vol. 25 (Feb, 1975), p. 3.
`Woodward, F. V.: “Mass identification-by photography and fingerprints,”
`The Police Journal. vol. 35 (1962), p. 91.
`Zeldenrust, ].: “Identificatie van slachtoflers bij rampen,” Tijdschrifi Voor
`De Politie. vol. 25 (1963), p. 241.
`'
`
`ment Bulletin. vol. 30 (July, 1961), p. 20.
`
`'
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`L
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`Chapter I”
`'
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`.
`ate”1: Fl n ge rp rI “15 a nd Grl me
`Sce n e P r0 cedures
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`34
`
`VALUE OF FINGERPRINT EVIDENCE
`
`LAW ENFORCEMENT OFFICERS and the general public associate
`fingerprint evidence with criminal investigations and the ap-
`prehension of criminals more than any other category of phys—
`ical evidence (Fig. 31). In fact, fingerprint evidence is applica-
`ble to almost all investigations; fingerprints are specific in that
`they prove the presence at a crime scene of the person who made
`the impressions and establish that a person once had contact with
`an evidentiary item.
`Unfortunately, fingerprint evidence and physical evidence in
`general are not sought after by investigators as diligently as they
`should be. The Science and Technology Task Force Report
`(President’s Commission, 1967) describes a Los Angeles case
`study of 626 burglaries in which a fingerprint technician was re-
`
`
`
`PROSECUTION
`
`(Evidence)
`
`
`
`IDENTIFICATION
`
`(Persons — Objects — Materials)
`
`Figure 31. The trilogy of evidence.
`111
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`l 12
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`Scott’s Fingerprint Mechanics
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`quested in only slightly more than 40 percent of all cases. No in-
`formation was available as to how many of the requests a tech—
`nician actually responded, but actual fingerprint evidence was
`produced in only 5 percent of the total cases.
`Peterson (1974) reports one study which revealed that, in one
`city, evidence was more frequently collected in offenses Where a
`suspect was already in custody, and in many cities, officers made
`an extra effort when they had a suspect against whom they could
`compare latent prints. Another study cited by Peterson revealed
`that of 749 cases examined in a medium—sized western city, 88
`percent were judged to have physical evidence at the scene, but
`fingerprints rated second in frequency of occurrence. The fore-
`going information is disturbing in that it indicates not that fin-
`gerprint evidence cannot be recovered, but that law enforcement
`officers are not properly processing crime scenes and seeking fin-
`gerprint evidence as diligently as they should.
`One fingerprint may establish the presence of the accused at
`a crime scene, and when presented as evidence in a case, it estab-
`lishes beyond a reasonable doubt the fact that the accused was
`at the scene, and it opens the way to a successful prosecution.
`Better yet, as so often happens, when a stolid, sullen uncoopera-
`tive individual who demands his Constitutional rights is con-
`fronted with fingerprint evidence, he is apt to change his atti-
`tude and tactics and admit the facts. Some defendants may elect
`to stand on their Constitutional rights, remain silent, and make
`it necessary to prove every point and every step in court. Fin-
`gerprint evidence is useful in this type of case.
`Fingerprint identification is pOSitive. A defendant may suc-
`cessfully convince a court that his fingerprints were placed at a
`crime scene when he was legitimately there, but he cannot suc—
`cessfully refute the identification of his fingerprints. Moenssens
`(1972) has pointed out that law enforcement agencies should
`not be uncooperative with defense attorneys who request to have
`fingerprint identifications checked by another examiner. Every
`qualified examiner who looks at the prints will come to the same
`conclusion. Rather than detract from the prosecution’s case, such
`additional examinations shOuld serve to strengthen it.
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`Latent Fingerprints and Crime Scene Procedures
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`113
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`An investigator should strive to obtain that one good bit of
`fingerprint evidence in every case wherein it is a factor, and con—
`versely, he should recover all possible fingerprint evidence even
`though at first it does not look too promising. It is better to have
`a selection, and when it comes time to use the evidence, he may
`choose that which he thinks is most useful. It often happens
`that a number of useful prints are developed, in which case the
`investigator is free to use what he thinks is the “best evidence,”
`disregarding but not discarding the rest.
`Fingerprint evidence is particularly useful in investigations of
`narcotics and other drug offenses. Not only may fingerprints as-
`sist in establishing possession of contraband, but they may also
`aid in establishing the identity of suppliers. Defendants may re-
`cant
`their confessions or flatly deny possession of prohibited
`drugs, witnesses may change their testimony, and courts may find
`an element of doubt in the prosecution’s case, but the positive
`identification of a suspect’s latent fingerprints may establish un-
`lawful possession of drugs beyond any reasonable doubt. Fin-
`gerprints may strengthen an already fine investigation, and they
`may even prove to be the difference between acquittal and con—
`viction.
`
`One important aspect of fingerprint evidence that is frequent-
`ly overlooked by the general public is that while fingerprints as—
`sist in the convictions of criminal suspects, they are also valuable
`evidence in establishing innocence. The identification of a latent
`print is not in itself proof of guilt nor can it be considered so
`until all other elements and facts of the case are considered by
`a court of law. Law enforcement agencies may develop sufficient
`information and evidence to charge a person with committing
`a crime, but only a court of law may determine guilt. Many in—
`dividuals are, however, cleared of any wrongdoing in the investi-
`gative stage, and latent fingerprints assist in establishing their in-
`nocence. Latent prints found at a crime scene and which are in
`such a position or location that only the perpetrator of the crime
`could have made them assist
`immeasurably in eliminating all
`other suspects.
`Fingerprint evidence may also aid an investigator in establish—
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`114
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`Scott’s Fingerprint Mechanics
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`ing ownership of stolen property. Quite often stolen property
`is found in the possession of a suspect, but a solid case cannot
`be established against the suspect because the property cannot be
`positively identified with the true owner. In such cases it is not
`necessary for the suspect to prove lawful possession, as the po—
`lice must prove that the property lawfully belongs to another.
`Latent fingerprints of the lawful owner developed on stolen
`property places the suspect in the position of accounting for the
`presence of the prints and,
`therefore,
`indirectly proving legal
`possession.
`Fingerprint evidence differs from most other physical evi-
`dence. One person and only one person can make a given finger—
`print impression. In this sense, fingerprints have both a positive
`and negative value—positive in establishing the identity of the
`person who made the impression and negative in that all other
`persons may be eliminated.
`
`35
`
`LATENT FINGERPRINTS
`
`Latent fingerprints are visualized by the layman as impressions
`made by the fingers on surfaces or objects which are handled.
`For all practical purposes, the conception is correct, but the fin-
`gerprint technician recognizes and deals with all degrees of la-
`tency from total invisibility to prints as good as impressions
`taken on paper for identification.
`The word latent mean “hidden” or not visible or apparent,
`but the word in a strict sense has no such limited application in
`the experiences of the fingerprint technician. In modern police
`usage, the term latent is applied to all chance or unintentional
`impressions that are of evidentiary value. Latent fingerprints are
`divided into two categories, invisible and visible. Invisible prints
`are made by perspiration and other substances on the skin sur—
`face and require the applicatiOn of a latent fingerprint
`tech-
`nique to develop the print so that it may be examined and pho—
`tographed.
`Visible fingerprints may be further divided into two classes:
`
`Latent Fingerprints and Crime Scene Procedures
`
`115
`
`plastic fingerprints and fingerprints made by contamination of
`the skin with such substances as blood, paint, ink, or grease, etc.
`Plastic impressions are molds formed by the friction ridges 1n
`soft pliable substances, for example, putty, modeling clay, axle
`grease, chocolate, butter, or soap, etc.
`.
`.
`.
`'
`Regardless of the nature of the latent print, Visible or 1n-
`visible, or whether it is a plastic impression or made by contam—
`ination of the fingers,
`the individual ridge Characteristics and
`their relationship to each other are the features essential for
`identification. If ridge structure is discernible and legible or can
`be so made with latent fingerprint techniques,
`the impressmn
`passes for a fingerprint for purposes of the fingerprint
`tech—
`nician; otherwise, it is considered a smudge or finger mark. livi-
`dential value of a fingerprint depends directly upon the indrvrd-
`ual ridge characteristics, which possess a sufficiency of clear de—
`tail to make a comparison with known prints possible.
`
`36
`
`PALMAR SWEAT DIFFERS FROM
`OTHER SKIN SECRETIONS
`
`There is a demonstrable difference between the secretion of
`the sweat glands on the papillary ridges of the hands and fingers
`and the secretions of the hairy portion of the body skin—the
`scalp, face, and neck, etc—which contains secretions of 'the se—
`baceous glands. Figure 32 depicts two pairs of fingerprints de-
`veloped by brush and powder, showing the difference between
`palmar sweat and sebum, the secretion of sebaceous glands, inso—
`far as its reaction to powder.
`The two impressions in Figure 32A were made by two fingers
`of a hand after it had been thoroughly washed and dried before
`it had made contact with any other skin surface or object. It IS
`seen that the print is “spotty”; the pore structure is revealed as
`a result of glandular activity. The powder adheres strongly 1n
`places and it leaves other places blank.
`.
`d
`After Figure 32A was made, the hand was washed, dried, an
`
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`116
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`Latent Fingerprints and Crime Scene Proaedures
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`117
`
`
`
`(B)
`(A) These two fingerprints were made by finger sweat.
`Figure 32.
`These fingerprints were made after rubbing the fingers on the neck below
`the ear..0ils from the sebaceous glands produce better impressions from the
`standpomt of development when using powders or fuming techniques.
`
`rubbed on the neck below the ear and the Figure 32B impres-
`sions were made. Result of powdering is a very even distribution
`of the powder particles over the ridges; pores are absent; and the
`ridges are complete, continuous, and strong. The latent impres-
`sions were made on the same surface under identical conditions
`and within a few moments of each other. The same powder was
`used to develop both sets of prints.
`Sweat glands, properly called eccrine glands, are found on al-
`most all surface skin areas of the body with their greatest den—
`sity on the palmar surfaces of the hands and the plantar sur—
`faces of the feet. Sebaceous glands are associated with the hair
`follicles. Sebum, the secretion of sebaceous glands, contributes
`oils and fatty substances to the film of perspiration on the skin-
`hence, the better adhesion of powder particles. Although there
`is a significant demonstrable difference between sweat and
`sebum, this knowledge is not of any great practical value to the
`fingerprint technician, as the choice of latent fingerprint tech-
`niques used depends more upon the nature of the surface to be
`examined.
`
`Modern instrumental chemical analyses have revealed that
`sweat is approximately 99.0 to 99.5 percent water, with the re-
`
`maining 0.5 to 1.0 percent being solids. About one half of the
`solids are organic substances and one—half inorganic salts. The
`predominant inorganic salt is sodium chloride (ordinary salt).
`The organic substances include a variety of acids and ni-
`trogenous compounds, the most important of which, for finger—
`print technicians, are amino acids.
`A complete description of the chemical composition of pal-
`mar sweat and sebum is essential for anyone wishing to conduct
`research programs for new,
`improved latent fingerprint
`tech-
`niques, but it does not have any significant practical value for
`the technician recovering fingerprint evidence. A technician
`should have a rudimentary knowledge of the techniques he uses
`and the substances they react with, but when dealing with finger-
`print evidence, it is the positive identification of a print that is
`of paramount
`importance, not
`the chemical processes of the
`techniques used. When testifying in courts as to the identifica-
`tion of fingerprints, a technician should not, regardless of his
`background and training, be drawn into a description of the
`chemical reaction between latent techniques and chemical sub—
`stances in the latent print residue. Such approaches by a defense
`attorney are aimed at confusing the jury and clouding the issue.
`Neither the chemical substances involved nor the nature of their
`
`processes have any direct effect upon identification of friction
`ridge characteristics.
`
`37
`
`FACTORS AFFECTING LATENT FINGERPRINTS
`
`Even with proper handling and application of the appropri-
`ate latent fingerprint technique, not all attempts to recover la—
`tent fingerprints are successful. Failure to recover latent finger—
`prints does not in itself necessarily mean that the prints were
`wiped off. The absence of latent fingerprints on an evidentiary
`item may be due to numerous factors, each depending on condi-
`tions existing before, during, and after the finger t0uched or
`handled the surface examined. Generally, the fingerprint tech-
`nician does not have any prior knowledge of these factors when
`
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`118
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`Scott’s Fingerprint Mechanics
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`Latent Fingerprints and Crime Scene Procedures
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`119
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`he processes the evidence for latent prints. However, an under-
`standing of the factors affecting latent prints aids the technician
`in explaining to laymen the fragile and transitory nature of la-
`tent fingerprints and why latent prints cannot always be re-
`covered.
`
`A latent fingerprint is a chance or accidental impression of the
`friction ridges of the skin. It is a reversed reproduction trans-
`ferred onto a receiving surface by a transferring medium. The
`transferring medium or method of transfer determines the type
`of
`latent
`impression—invisible print, plastic impression, etc.
`The factors affecting a latent fingerprint may be grOuped into
`three stages in the formation of a latent print: pretransfer con-
`ditions
`(subject factors),
`transfer conditions
`(transposal
`fac-
`tors), and pOSt-transfer conditions ( environmental factors). All
`these factors are relative, and rarely are conditions identical in
`two separate cases. Knowledge of the factors assist
`in under—
`standing the fragile and elusive nature of latent impressions
`and are presented for this purpose rather than as an aid in re-
`covering latent prints or for identification. More often than not,
`the factors are cumulative in effect and the isolation of any one
`factor as the direct cause for the lack of latents is impossible.
`
`SUBJECT FACTORS
`
`Subject factors apply to the subject making the latent impres-
`sions and are the most variable of all factors affecting latent
`impressions, as they vary not only between individuals but from
`day—to-day for the same individual. The observations are gener-
`al
`in nature and do not purport to apply in every individual
`case. It is not possible to determine the age, sex, or race of an in-
`dividual solely from their fingerprints.
`AGE. Senile atrophy of the skin starts shortly after the age of
`forty. The epidermis becomes thinner at
`the expense of the
`lower strata;
`the papillae of the dermis flatten and lose their
`elastic fibers; and numerous creases appear in the friction ridge
`skin areas._ Certain diseases associated with aging may afiect the
`friction ridges. Deterioration of the skin produced by age is not
`in itself necessarily the cause of a disease; simply, the longer one
`
`lives, the greater the chance of meeting with a disease~producing
`set of circumstances.
`
`The response to thermal sweating is slower for older persons,
`and it is also slower to return to a normal rate. The rate of in-
`
`sensible sweating is also lower than in younger persons. After the
`age of forty, the sebaceous glands are reduced in number of ac-
`tive glands, and the glands show certain qualitative changes. In—
`dividuals over twenty-five years of age appear to secrete lower
`concentrations of amino acids than younger subjects (Edwards
`et al., 1966). These briefly described characteristics of the effects
`of aging tend to indicate that there is a diminished probability
`of success in recovering latent impressions of very old individ—
`uals.
`
`SEX. Several factors based on sexual differences may affect la—
`tent fingerprints. Statistically, in young adults, the friction ridges
`of women are significantly finer (or narrower)
`than those of
`men (Cummins and Midlo, 1943). Fine ridges may also be
`found in the very young and the very old, and manual labor has
`a tendency to strengthen ridges;
`therefore, no attempt should
`ever be made to identify a latent print as a woman’s solely on
`fine ridges. The effect of fine ridge structure on latent impres-
`sions is obviOus; less skin surface touching the receiving surface
`leaves less latent print residue to react with latent fingerprint
`techniques and is accordingly, spotty in appearance.
`Women tend to perspire at a lower rate than men, although
`they have greater densities of heat-activated sweat glands per
`square centimeter, and the concentration of sodium chloride 18
`lower for women. Anyone who has examined a number of fin-
`gerprints soon notes that there is a significantly greater number
`of creases in the fingerprint pattern areas of women. Creases
`may be found in the fingerprints of men, especially with increas-
`ing age, but are common in those of women. It is not uncom-
`mon to find fingerprints of women that cannot be properly
`classified because of creases and fine ridge structure.
`STIMULI. There are three types of sweating:
`thermal, emo-
`tional, and gustatory sweating. Each is induced by a different
`type of stimuli. Thermal sweating is stimulated by warmth,
`ex—
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`120
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`Scott’s Fingerprint Mechanics
`
`ertion, nausea, fever, and drugs. Its effect on latent fingerprints
`depends on the rate and duration of sweating and the acclimati-
`zation of the subject. Excessive thermal sweating adversely af-
`fects latent prints as there is too much moisture of the fingers,
`and the latent appears as a blurred image. Emotional sweating
`is stimulated by anxiety, tension, or pain—conditions most like-
`ly to be present for a subject when committing a crime. Emo-
`tional sweating could possibly aCCOunt for the majority of latent
`prints recovered from crime scenes. Gustatory sweating is in-
`duced by eating spicy foods and has little application to latents
`at crime scenes.
`
`OCCUPATION. Occupational effects on the skin condition of
`subjects has been discussed in Section 28. However, occupation
`may also affect the subject, concerning his rate and duration of
`perspiration. During the hot summer months, persons who work
`in cold storage and other relatively cold areas have little oppor—
`tunity to acclimatize to warm weather. Such persons may sweat
`profusely when outside of their occupational environment. Con-
`versely, during the cold winter months, persons who work in a
`hot and humid occupational environment do not perspire as
`readily as those acclimated to the lower temperatures.
`MEDICAL CONDITION. The medical condition of the subject
`may affect both the physical condition of the skin and sweat
`gland activity. Examples of diseases which may affect friction
`ridges
`are:
`dermatitis venenata,
`tinea, verrucae,
`scabies,
`pompholyx, keratoderma palmare et plantare, erythema multi—
`forme, syphilis, dermatitis repens, carcinoma, melanoma, ar-
`senical keratoderma, and gonorrheal keratoderma. Certain dis-
`eases and the medical treatment for some diseases may also af—
`fect the rate, duration and chemical composition of sweat.
`
`TRANSPOSAL FACTORS
`The most significant transposal factor having an effect on Ia-
`tent fingerprints is the nature of the receiving surface. Very
`rough surfaces may retain the deposits of latent print residue,
`but the nature of the surface may make distinguishing of ridge
`characteristics impossible. Extremely soft substances may be so
`
`Latent Fingerprints and Crime Scene Procedures
`
`121
`
`sticky that much of it adheres to the fingers, thereby destroying
`any plastic impressions that the ridges may have made in the
`substance. Contaminants on the hands may be so heavy that too
`much material is deposited and the ridge impressions obscured,
`or in some cases heavy concentrations of contaminants on the re-
`ceiving surface may also preclude the possibility of latent fin—
`gerprints; well-oiled firearms is one such example. Extremely
`porous surfaces and substances with a high coarse-fiber content
`may also prove to be a poor receiving surface for latent prints.
`Transposal factors also include the manner
`in which the
`friction ridges come into contact with the receiving surface. Cer-
`tain objects may be handled in only one manner, while others
`are constructed in such a way that direct grasping is impossible.
`The am0unt of pressure may also be a factor in that too great
`a pressure may destory ridge details, and prolonged contact of
`the fingers with the receiving surface may blur the latent impres-
`sion because of the increased deposit of sweat.
`
`ENVIRONMENTAL FACTORS
`
`Environmental factors may be defined as those conditions and
`situations to which a latent fingerprint is exposed after its de—
`posit on a receiving surface. Temperature, humidity, and han-
`dling are the three primary factors within this grOup which may
`adversely affect a latent fingerprint. Time may also be considered
`a factor and is an important consideration both from the inves-
`tigative viewpoint and for the successful recovery of latent
`prints. However,
`time is not in itself a factor affecting latent
`prints; quite simply, the longer the period between deposit of
`the latent until it is processed, the greater its exposure to temper-
`ature, humidity, and handling.
`TEMPERATURE AND HUMIDITY. AlthOugh temperature and hu-
`midity may be measured independently, their effect upon latent
`fingerprints is interdependent With each other. Bluhm and Loug-
`heed (1968) fOund that the ideal temperature—humidity condi-
`tion for preserving latent fingerprints on a nonporous surface
`is 40° F and 55 percent relative humidity. Latent prints on non-
`porous surfaces deteriorate faster at
`temperatures exceeding
`
`
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`

` l lil lli l 5
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`'700 F and corresponding relative humidity of 25 percent or less
`than latent prints at lower temperatures. Excessively high tem-
`peratures with corresponding low relative humidity tend to dry
`Out a latent print through evaporation of the moisture content.
`Exposure of latent impressions to adverse temperatures and
`humidity conditions may indicate a lower probability of success-
`fully recovering, good latent prints but does not necessarily mean
`that all such impressions cannot be successfully recovered. High
`concentrations of sebum and other chemical substances may pro-
`long the life of a latent under such conditions.
`Another situation in which temperature and humidity may ad-
`versely affect latent prints is the temperature of the object on
`which the latent is located in relation to the surr0unding air. If
`an object is taken from a cool environment and placed in a
`warm environment, for example, a pistol found in a driveway
`is brought into the house for examination, the object tends to
`“sweat” as condensation forms on it. Such sweating of an ob-
`ject tends to wash away any latent print residue. Evidentiary ob-
`jects found outside in unprotected areas must be protected from
`the weather. Dust, dew, and rain may obscure or completely
`eradicate latent fingerprints. Latents may also be destroyed by
`strong sunlight or heat.
`_
`Improper and excessive handling of evidentiary items probab-
`ly destroys more latent fingerprints than any other factor. Fin—
`gerprint evidence must be carefully protected even after latent
`prints have been developed. Tests conducted at the United States
`Army Criminal Investigation Laboratory, Fort Gordon, Georgia,
`indicate that latent impressions are more easily damaged after
`they have been developed with powder than before processing.
`The most critical period in preserving fingerprint evidence is
`during removal from the crime scene to the laboratory or identia
`fication bureau. The investigator must take all appropriate mea—
`sures to protect all surfaces bearing latent impressions while
`transporting the evidence.
`
`122
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`Latent Fingerprints and Crime Scene Procedures
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`123
`
`38
`
`HOW LONG D0 LATENT FINGERPRINTS LAST?
`
`the life of latents is con-
`In the mechanics of fingerprints,
`sidered as that time in which the impressions may be processed
`or developed to a point of usefulness from an investigative
`standpoint and for evidentiary purposes.
`All the factors cited in Section 37 and their cumulative effects
`determine the life of a latent impression. Latent prints ordinar-
`ily remain for several days in a condition in which they may be
`readily processed, but as time passes from the instant of impres-
`sion,
`their acceptance of powder diminishes until a point
`is
`reached when insufficient powder adheres to reveal enough detail
`to make an identifiable fingerprint. The first
`twenty—four or
`thirty—six hOurs appears to make no appreciable change in recep-
`tivity to powder for latents on nonporous surfaces. Prints may
`be developed by powders to a better advantage an hour or two
`or
`several hours after
`they are made,
`than if
`they are
`powdered immediately after being made.
`For good acceptance of powder,
`latents should be free of
`visible particles of moisture, which are usually present in latents
`immediately after they are made. Better ridge detail is revealed
`after the excess moisture has evaporated. Excessive moisture in
`a fresh print holds an excessive amount of powder. Conversely,
`there are times when the latent print is dried out and is not re-
`ceptive to powders. In such instances, the investigator may blow
`onto the surface while he is applying the powder, as his breath
`adds the necessary moisture to the latent print residue. When
`using the breath technique, the object examined must not be too
`cool or the investigator’s breath forms moisture over the entire
`surface and the powder paints the surface,
`thereby obscuring
`any latent prints.
`If latent impressions are subject to ideal environmental condi-
`tions, they may last indefinitely. In one case, the Pittsburgh Po-
`lice Department was able to develop and lift good latent prints
`
`

`

`124
`
`Scott’s Fingerprint Mechanics
`
`Latent Fingerprints and Crime Scene’Procedures
`
`125
`
`from a metal box that had been in storage for eight years (“La-
`tent Prints, 8 Years Old, Help Solve Bizarre Murder,” 1963).
`Good latent prints have also been developed by the ninhydrin
`technique on records that have been sealed for thirty years
`(Svenssen and Wendel, 1965). These are unusual
`instances
`where the evidentiary items were not subjected to adverse condi—
`tions and cannot be expected to be normally found—as fresh
`prints represent one extreme, these cases represent the other. In
`actual practice, if nonporous surfaces are not processed within
`a few days, there is a reduced chance of obtaining good latents.
`However,
`two aspects must be stressed: Latents may last for
`quite lengthy periods on porous surfaces, such as paper, and be
`recovered with appropriate chemical techniques, and an attempt
`should always be made to develop latent impressions, regardless
`of the time lapsed since the time of the offense. The factors af-
`
`
`
`five-month-old latent developed on glazed surface. Latent was “dated” by
`scar showing in the inked impression, which was known to have been made
`five months previously.
`
`fecting the life of latent prints are so numerous and varied that
`it is not possible to determine the likelihood of their presence
`unless a thorough examination has been made (Fig. 33).
`
`39
`
`LATENT FINGERPRINT TECHNIQUES
`
`A latent fingerprint technique is any method, process, proce-
`dure or technique used to intensify or enhance latent fingerprint
`impressions for
`identification purposes. Techniques may vary
`from observation under a strong light to the application of ra-
`dioactive chemical compounds. Chapters V through VIII cover
`latent
`fingerprint
`techniques and their preparation and use.
`Some of the techniques have been used to connect offenders with
`crime scenes, others are relatively new, while still others are novel
`and have little or no practical value. Some are experimental, and
`their practical value has yet to be established. As many tech-
`niques as possible are listed in order to acquaint and familiarize
`the reader with all possible techniques for recovering latent im-
`pressions.
`No single latent fingerprint technique should ever be adopted
`to the complete exclusion of all others. Each has its time and
`place applicable to particular situations and circumstances. For
`example,
`the normal procedure for developing latent
`impres-
`sions on paper is application of the iodine technique, then nin-
`hydrin, and finally silver nitrate, in that order. However, in one
`specific case, only the iodine technique could be used because the
`evidence was counterfeit currency supplied by an informer and
`had to be returned by the informer to the suspect without any
`traces of processing. In this case, the iodine technique was used,
`the latents photographed, the iodine cleared, and the counterfeit
`currency returned without the suspect’s knowledge, thereby aid-
`ing not only in the apprehension of the counterfeiters but also
`their distributors.
`
`“Regardless of the technique used, it should be re