Kirk, Paul L.

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Journal of Criminal Law and CriminologyVolume 40 | Issue 3 Article 81949Microscopic Evidence--Its Use in the Investigationof CrimePaul L. KirkFollow this and additional works at: https://scholarlycommons.law.northwestern.edu/jclcPart of the Criminal Law Commons, Criminology Commons, and the Criminology and CriminalJustice CommonsThis Criminology is brought to you for free and open access by Northwestern University School of Law Scholarly Commons. It has been accepted forinclusion in Journal of Criminal Law and Criminology by an authorized editor of Northwestern University School of Law Scholarly Commons.Recommended CitationPaul L. Kirk, Microscopic Evidence--Its Use in the Investigation of Crime, 40 J. Crim. L. & Criminology 362 (1949-1950)MICROSCOPIC EVIDENCE-ITS USE IN THEINVESTIGATION OF CRIME*Paul L. KirkPaul L. Kirk, Ph. D., Professor of Biochemistry, University of California MedicalSchool, is a nationally recognized expert on microscopic evidence and its applicationsto the solution of crime. Over a period of years Professor Kirk, who is one of ourAssociate Editors, has contributed papers on various problems of microanalysis tothis Journal and has appeared as an expert witness on these problems in numerouscourts. His current paper, which should be of particular interest to progressivelyminded investigators and police microanalysts, describes several pieces of specialequipment for the thorough collection of microscopic evidence found at crime scenesor on the clothing of suspects.-EDIToR.The use of microscopic evidence in the investigation of crimehas become progressively more -important in recent years inAmerica. Not only has considerable progress been made in theidentification and study of hairs, fibers, glass and metal frag-ments, soil, and many other forms of fine debris, but it has beenmore generally appreciated that this type of evidence is usuallypresent in most crimes even when the larger and more obviousitems have been lost or their possibilities exhausted.This fact, coupled with the well known circumstance that evi-dence is rarely found in large quantity, or evidential materialsin a form suitable for the ordinary or macromethod, emphasizesthe growing importance of the microchemist in the field of crim-inal investigation. While this is indisputable, it is unfortunatelytrue that many law enforcement agencies consider that namingan individual to the position of "microchemist" automaticallyqualifies that individual to do microchemical examination, re-gardless of his training or experience. In point of fact, rela-tively few of the criminalists currently employed by these agen-cies are truly competent microchemists, however capable theymay be in general. Even more unfortunate is the regrettabletendency for the "classical," or "official" method adopted bysome organization such as the Association of Official AgriculturalChemists, to be required by attorneys and court officials, as theonly acceptable examination procedure. While there is no apriori objection to the choice of an old and well establishedmethod which has been tested over a long period and is wellunderstood, it is often true that such a method is markedly in-ferior to a newer procedure which may be more sensitive, moreaccurate, or more specific, or all of these together. To considerthe matter otherwise is to deny the validity of progress in thefield. It is a curious fact that a poison separation procedure* Supported in part by a grant from the Research Board of the University ofCalifornia.MIGOSCOPIC EVIDENCEsuch as the Stas-Otto method, which is so antique (over 100years) that to claim it as the best possible procedure automati-cally denies that serious progress in the field is possible is stillconsidered in many quarters as the best possible procedure.Another more immediate application of this curious situation isthe frequent insistence by attorneys that the Gutzeit method fordetermination of arsenic be used because it is the "official" and"standard" method. It has been known for years that themethod is grossly iniaccurate as a quantitative method, andscores of papers have been published detailing the sources oferror and uncertainty. Moreover, it is less sensitive thannumerous superior procedures which have appeared, but whenthe latter are used as the basis of testimony, doubt is cast onthem bqcause they are not the "standard" method.In the field of micromanipulative technique in handling andexamining microscopic evidence, it is fortunate that no long-standing traditions and prejudices require eradication. Therehas not been any "standard" method for the collection, sorting,and examination of the solid and liquid debris and traces thathave assumed constantly greater significance as more was donewith them. It is the primary purpose of this communication tooutline some useful procedures for handling, storing, and manip-ulating minute amounts of solid and liquid evidence of the typesfrequently encountered in criminal investigation. It is hopedthat as real improvements are found, they will not be disregardedbecause of the priority of any methods described here.hICIDENCE OF MIcRoscoPIc EvmmL-cEMicroscopic evidence is carried particularly by the clothingof the perpetrator in most instances, and by the clothing of thevictim in cases involving direct damage to, or contact with a vic-tim. It is virtually impossible for a burglar to break into a build-ing without accumulating in his pockets, pants cuffs, and on thesurface of his clothing a number of significant small fragmentsof the materials damaged by him in effecting an entrance. Inassaults, murders, rapes, and kindred crimes, contact betweenthe criminal and his victim is the rule, and always leads to theinterchange of fibers, hairs, dusts, and fragments -of microscopicdimensions. In addition to clothing, the finger nail scrapings,ear wax, shoe soles, and other likely places accumulate traces ofsimilar materials. It is the belief of the author, as a result ofyears of study of this type of evidence in many varieties ofcrime, that only a minute percentage of such evidence is everexploited even to a reasonable extent, and that the majority of19491PAUL L. KIKunsolved crimes are those in which this type of evidence wasentirely or partially neglected.It is easy for the investigator to look for the obvious, i.e. thegun that shot the victim, the tool that opened the safe, the largeitems of clothing torn from a victim, or other large and apparentitems of evidence, while overlooking the fact that the minute evi-dence of which both perpetrator and victim were unaware willremain after the larger objects have been hidden, discarded, ordestroyed. In fact, it is so simple to collect from the clothing ofboth victims and suspects a considerable amount of such evidencethat it is surprising how limited these collections usually are.Even criminalists occasionally destroy such evidence deliber-ately or accidentally while concerning themselves with the moreobvious items. While this may be a natural action, it is an un-fortunate one that should be discouraged. As an example of theapplication of the principles of microscopic evidence examina-tion can be cited instances in which a gun which has shot a victim,or a knife which has stabbed one, is discarded with the body. Itis useless then to stop with the proof that this is the weaponresponsible for the injury, since the ownership of the weapon isthe vital matter at issue. Microscopic evidence carried in thevarious recesses and openings of the gun or the knife may oftenbe sufficient to prove that it was carried in a certain pocket of aparticular suspect, by comparison of the materials on the weaponwith those in the pocket.COw=CTION OF MCROSCOPIC EVIDENCES6derman and O'Connell mention briefly in their book "Mod-ern Criminal Investigation" a vacuum filter by means of whichclothing may be cleaned to recover from it the dust, debris, andsimilar microscopic evidence. The description is not detailed,and to the author's knowledge there has not been available com-mercially any good model of such a device. Clearly this type ofinstrument is useful not only for cleaning of debris from cloth-ing, but from window sills over which burglars have climbed,automobiles, both inside and outside, when they have figured incrime, and in general, scenes of crimes in which contact of vari-ous kinds with the criminal has occurred.A useful vacuum sweeper filter which is constructed with rea-sonable ease and is commercially available' is shown in Figure 1.It is made from a clear methacrylate plastic which allows unim-peded vision through it at all times and is strong and durable. Itis made in two sections which attach at the center by means of a1 Obtainable from the Microchemical Specialties Co., Berkeley, Calif.[Vol. 40MICROSCOPIC EVIDENCEFigure 1.bayonet or screw connection which is readily opened. In one sec-tion is mounted a screen on which is placed an ordinary filterpaper which serves as the filter to collect all materials removedfrom the evidence source. This section is attached to any goodvacuum sweeper by means of a rubber hose furnished with thesweeper. The other section carries the sweeping nozzle properwhich is not too large to allow the application of a good vacuum.-It is passed over the clothing or other object to be swept, and ina matter of minutes -will accumulate much more evidence thancould be directly removed by forceps and visual inspection inmany hours of labor.In use, the vacuum filter is passed over clothing, inserted intopockets and pants cuffs, or passed over other surfaces whichmay contain microscopic evidence. All sweepings are collected onthe paper filter, a new one being used each time.A vacuum sweeper and filter installed in an interrogation roomat a police department could in about 5 minutes collect nearlyall significant microscopic materials from the clothing of a sus-pect being questioned. If the latter is released for lack of evi-dence, he does not remove the significant debris with him to belost or desioyed. If examination of the debris later implicatesthe suspect, as frequently has happened, the latter may be againtaken into custody. If it does not, the amounts involved are read-ily destroyed. The expenditure of time is vastly less than thatused in interrogati6n, much of which is often fruitless. Theknowledge that he is definitely implicated by the microscopicevidence has often resulted in confessions-and guilty pleas, thusdemonstrating the essential economy of this method of investiga-tion. The cost of installing a sweeper device is insignificant bycomparison with almost any of the other costs of criminal inves-1949]PAUL L. KIRKtigation, and there is no valid reason for failure in its generaladoption. Necessarily, laboratory examination of the collectedevidence remains to be performed, but the department whichlacks a laboratory can in most cases obtain such services fromstate laboratories, neighboring city police laboratories, or pri-vate laboratories. Without the evidence, no laboratory can pro-vide helpful information, and when the police officer allows asuspect to carry out with him evidence which otherwise mightprove his guilt or innocence, it is indeed a situation calling forcorrection.STORING OF SoLm EVIDENCEMicroscopic evidence collected in the sweeper is stored by un-loading the sweeper as follows: The nozzle of the filter is placedinside a cellophane envelope which is held tightly around it sothat no debris can escape. The loose material in the chambermay be largely tapped down into the cellophane envelope in ad-vance. Still holding the nozzle in the left hand the sweeper isdisattached at the center and the paper is allowed to fall into thebottom compartment. This is folded and pushed down throughthe nozzle into the cellophane bag with a small brush, preferablya good grade camel's hair artist brush. The dirt and debris re-maining is then carefully swept down through the nozzle into thebag taking care that any adhering dirt on the inside of the nozzleitself is detached and falls into the bag. A label placed on thebag identifies it as to source, and the entire cellophane envelopemay be readily stored.If there is occasion for preliminary examination under themicroscope it is desirable then to transfer the sweepings to aclear flat dish. This may be a glass Petri dish of the type usedby bacteriologists which can be stacked, and which, being clear,allows visual examination of the contents. An alternative whichis both less expensive and more satisfactory is the use of a flatplastic dish of similar dimensions. Such plastic dishes can beobtained with tight fitting covers which do not fall off readily asdoes the Petri cover and the dish is not subject to breakage. Itis also clear and can be stacked in the same manner as the Petridish. Storage in these dishes for considerable periods of time isboth simple and convenient inasmuch as they stack in a smallspace and are readily labeled and easily examined as to contents.The filter paper is usually brushed off into the dish and dis-carded at the time of transfer from the cellophane bag.[Vol. 40MICROSCOPIC EVIDENCEPRELDUNARY SORTING OF EVIDENCEThe evidence which has been collected and stored may now besubjected to preliminary observation to ascertain its generalcontent. If this is of a tentative nature only it may be doneTOP VIEW SIDE VIEWFigure 2.directly through the dish by visual means with or without mag-nification. Sorting, however, requires microscopic observationunder low powers of the stereoscopic binocular microscope, andit cannot be carried out through a lid. Very convenient for sort-ing is the use of the plastic sorting dish' shown in Figure 2. Itconsists of a relatively large central chamber which is sealedwith a clear flat lid and has sufficient capacity to contain the ordi-nary sweepings from a man's suit. All of the sweepings aretransferred to this central chamber before sorting them. Aroundthe center is arranged a series of 7 smaller chambers 5/8 inchin diameter and 3/16 inch in depth. Over these chambers isplaced a tight fitting ring carrying one hole only, the diameterof which is the same as the chambers. By rotating the ring, thehole may be placed over any chamber thus opening that one andsealing all the others. This avoids any possibility of contamina-tion of the evidence except in the single open well. When the holeis rotated to the blank region, all the wells are sealed tightly, toretain evidence in them and to prevent all possibility of contami-nation. The examiner may remove the contents of any singlewell for mounting and examination, again having only onl openat a time.Significant evidence is stored by categories in the outsidechambers, e.g. paint flakes in one, glass in another, metal frag-ments in another, blue wool, brown wool, etc. in others, until allimportant categories of evidence are isolated. A single labelidentifies the case and source of all evidence in the dish. As199]PAUL L. KIRKmany dishes are used as necessary, and they may be stacked in aminimum of space with no chance of confusion, loss, or contami-nation. The alternative use of separate dishes for each categoryof evidence leads to large numbers of containers, losing of labels,occupancy of excessive space, and sometimes even to mixing orloss of evidence.MA1uAL HANDLING OF SOLID EVmENCETo separate a single small fiber or fragment of glass from amass of debris is not a simple operation unless the tools used forthe separation are suitable. Forceps are usually employed, butnearly all forceps available commercially are unsatisfactory.Any forcep having a corrugated tip does not operate well inmanipulating most small pieces of evidence. This eliminates theuse of the common dissecting forcep which is designed to graspsoft tissues, not small solid objects. The jeweler's jewel forcephas a smooth finely pointed tip, thus being superior both to thedissecting and the cover-slip type of forcep. In the absence of ajewel forcep, it is possible to use another type after polishingoff the corrugations and grinding or filing the tips to a narrowpointed end with a good flat contact. This may be done withalmost any well constructed forcep, but is less simple than usingdirectly the jewel forcep.At times, very minute fragments cannot be grasped with theforceps at all, because of their size. When this is true, a needlewhich has been passed between the fingers to deposit a very thinfilm of grease is useful. The object will usually adhere to theneedle tip and may be transferred. Ordinary dissecting needlesare not suitable because of their coarseness. A fine sewing needlemounted in a wooden handle is preferable. The finest needlesmay be constructed from tungsten wire which has been pointedwhile hot with solid sodium nitrite. Needles of this type are stillvery sharp and sufficiently rigid at dimensions so small that asteel needle of the same size would be too fragile to use, andalmost impossible to make.MAUAL HANDLING OF LIQUIDSLiquid evidence is less frequently encountered than solid andnever in vacuum sweepings. It does at times occur and in verysmall volume. Furthermore, the addition of small volumes ofliquid reagents in carrying out tests is a frequent operation whichis very familiar to the microchemist. Most instructions callmerely for a crude pipet drawn from a piece of glass tubing,filled by mouth suction, and emptied by gravity or blowing. This[Vol.*40MICOBSCOPIC EVIDENCEtechnique is often very awkward and may lead to getting evi-dence or reagents in the mouth, and usually involves a relativelack of control of the flow of liquid.---- ---Figure 3.Good technique in handling small volumes of liquid involvesthe use of a control on the pipet to apply suction or pressuremore accurately than is done by the mouth. While a rubber tubeto the mouth is an improvement, and a rubber bulb is useful,a syringe type control' such as that described by Sisco, Cunning-ham and Kirk (1) is more useful. With it, the liquid flow isunder careful control, and unlike a rubber bulb, removal of thepressure does not cause variation of pressure in the pipet. Animproved design of this control is shown along with two types ofpipet in Figure 3.The pipet may be designed for qualitative work, i.e. when thevolume taken is not important, or for quantitative work, in whichcase it is necessary to know the volume. In the former instance,the pipet is drawn from glass tubing to a rather fine tip at oneend, and a thickened taper at the other to fit the control. Thequantitative pipet must be made from capillary tubing, markedand calibrated as shown. It may be used with rinsing to measureaccurately volumes as small as 0.005 ml. Most liquids used bythe criminalist are added in unknown volumes as qualitativereagents, and the qualitative pipet serves adequately for mostpurposes.One further type of pipet is useful for qualitative addition ofreagents when the volume needed is extraordinarily small, i.e.less than 0.001 ml. It consists of an extremely fine tip drawn froma fine, heavy walled capillary such as a thermometer tube. Manip-ulation of such a pipet is best achieved by use of the mouthblowing tube because the bore of the pipet tip is so fine that con-siderably pressure or suction is required to cause any movement,and under these circumstances, both syringes and bulbs are un-satisfactory. Some skill is required to construct this type ofpipet, and its uses are distinctly limited.1. Sisco, R. C., Cunningham, B. and Kirk, P. L., J. Biol. Chem., 139, 1 (1941).1949]

Microscopic Evidence--Its Use in the Investigation of Crime

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Microscopic Evidence--Its Use in the Investigation of Crime

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