Davis, Charles A.

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Northwestern University Illinois, School of Law: Scholarly Commons

Journal of Criminal Law and CriminologyVolume 50Issue 3 September-October Article 16Fall 1959Notes on Physical Evidence in Pedestrian Hit andRun AccidentsCharles A. DavisFollow 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 CitationCharles A. Davis, Notes on Physical Evidence in Pedestrian Hit and Run Accidents, 50 J. Crim. L. & Criminology 302 (1959-1960)NOTES ON PHYSICAL EVIDENCE IN PEDESTRIAN HIT AND RUN ACCIDENTSCHARLES A. DAVISThe author holds the rank of Lieutenant in the Indiana State Police and is Director of their policelaboratory. His field of specialty in the laboratory has been chemistry. Lt. Davis has contributed tothis Journal on several occasions and has recently been appointed chairman of Indiana's newly or-ganized Commission on Forensic Sciences.-EDOR.The pressure of public opinion generated by ahit and run accident causes an urgency on the partof the investigators which may result in the loss ofvital physical evidence. This is true in casesinvolving fatal accidents as well as personalinjury. The investigation starts with the body ofthe victim. If the victim is still alive, a littleplanning will prevent the loss of trace evidencethat may be present on the body of the victim oron the victim's clothing. The trace evidenceusually consists of paint chips and/or paintsmears, metal fragments, glass fragments, and anassortment of miscellaneous traces.The first -loss of evidence is most often sustainedwhen the body is first moved. The method ofpreservation of evidence is exactly the same for aninjured victim as it is for a dead victim. Beforemoving the body a clean sheet should be placedon the cot or stretcher which must be as close tothe victim as possible. After placing the body onthe sheet, the sheet should be wrapped around thevictim. The purpose of the sheet, of course, is tocatch any particles that may fall from the victimor his clothing. To prevent the loss of evidence inthe receiving room of the hospital or at the mortu-ary, the attendants must be acquainted with theinvestigator's problem.The second loss of evidence is usually sustainedwhen the clothing is removed from the body. Whenthe body is transferred from the stretcher or cot tothe examination table, the sheet should be keptwrapped about the body. During removal of theclothing, the sheet should be held out on each sideof the body as far as practical; the edges of thesheet must be held high enuogh so that a pocketis formed, catching the debris from the clothing asit is removed. Never premit clothing to be cutthrough a hole that already exists. Later, a pieceof cloth or a few threads may be located on thesuspect's car which could be fitted into the hole ifit remains intact..As the clothing is cut or otherwiseremoved from the body, it should be kept over thesheet. Any visible dirt on the body should bebrushed onto the sheet before the body is moved.After the body has been lifted from the sheet, thefour corners can be gathered together and tied;all of the dirt, debris, and the victim's clothingare ready to be taken to the laboratory for exami-nation.At the laboratory the sheet must be spread outto dry immediately, and the clothing separatedfor faster drying. Clothing wet with blood orwater should never be kept in a package for morethan an hour. It should be spread out to dry assoon as possible by the investigator if immediatedelivery to the laboratory is impractical, and whendry, again packaged to prevent loss during trans-portation.At the laboratory after the debris is removedfrom the clothing by careful brushing over thesheet, there is usually a sizeable pile of sand,earth, dust, fibers, vegetation, glass, and metalfragments on the sheet. The gross pieces are re-moved for possible comparison with like materialwhich may have broken from the suspect's carwith the impact (figure 1). Care should be takento protect the fragile detail on the fractured edgesso that they will be suitable for jigsawing intopieces from the suspect's car. Since headlamps onmodern vehicles are interchangeable units, themake of the vehicle usually cannot be determinedfrom fragmentary remains of headlamps. Thelenses of the parking lamps can usually be associ-ated with certain makes and models of vehiclesas may decorative chrome strips, hood ornaments,headlamp rims, and door handles. All glass, metal,and plastic fragments found at the scene should bepreserved for future comparison. Even though theheadlamp fragments cannot-lead the investigatorto the make and model of the vehicle involved, itmay be possible to identify a fragment found atthe scene as having come from the suspect's carif broken pieces are found on his car for comparison.A detailed examination of the fine debris fromPHYSICAL EVIDENCE IN HIT AND RUN ACCIDENTSFigure 1Typical damage to vehicle wvhich struck pedestrian. Note area where paint is chipped free from metal.the clothing is conducted with the stereoscopicmicroscope (figure 2). The principal object of themicroscopic search is for paint chips. The paintchips on the victim's clothing come from placesFigure 2Debris removed from victim's clothing. Paint chipsvisible only with microscopic aid.where the impact buckled the metal at a sharpangle. This bending of the metal causes the paintto craze and chips break free from the supportingsurface leaving the metal bare. Paint chips freedin this manner are often very small and may evenbe subvisible; yet with the aid of a microscopelayer structure, layer sequence, color, and eveninclusions may be observed (figure 3). The softeror woolier surfaces of the clothing are likely toretain paint chips in greater quantities than hardersurfaces.When paint samples from the suspect's car arecollected for comparison purposes, they should becollected from each place where the metal has beenFigure 3Paint chip comparison as seen through compoundmicroscope.CHARLES A. DAVISbent and the paint has crazed leaving the metalbare. Fenders are often repainted, and during therepair process, paint is sanded off completely inonly a few places; a fender so repaired and re-painted will have different layer structures atdifferent places on it. Paint also varies in thicknessat various places on the vehicle and for comparisonpurposes should come from the same vicinity onthe vehicle as the chips that may be found on thevictim. If chips are collected from all places on thesuspect's vehicle where bare metal is observed, theinvestigator then is assured of having some chipsfrom the same vicinity as any found on the victimor at the scene. The chips collected from differentplaces on the suspect's car may be placed in onecontainer; a small vial with a screw cap is ideal.One case comes to mind in which an investigatorfound a large chip or scale of paint at the scenewhich was jigsawed into a sample piece removedfrom the suspect's car for comparison purposes.Search for large chips or scales of paint at thescene should not be neglected.Paint chips from the suspect's car are bestcollected by using a knife blade to loosen chipsfrom the edges of paint at the location of baremetal. Paint scraped from a flat surface by a knifeis not so valuable as chips pried loose where theyhave already been partially separated by thebending of the metal. Two chips may be mountedtogether on a microscope slide for stud- with acompound microscope; one chip recovered fromthe victim and one chip from the suspect's carmay be mounted on the same slide. When properlyprepared, a photomicrograph of the slide in colorprojected on a screen in court makes a very gooddemonstration.The slide may be prepared by building it "upsidedown." Place a square cover glass on the table.Affix with permount a piece cut from the end of aregular microscope slide; the length of this pieceshould be half the width of the cover glass. Placethe ground edge (the end of the piece of slide) inthe middle of the cover glass. These can be pre-pared in advance so they will be dry enough tohandle when needed. Apply a tiny drop of per-mount to the cover glass at the ground edge of theaffixed portion of the slide in the center of thepreparation. Immediately place a chip of paintrecovered from the victim into the drop of per-mount with the surface layer against the groundedge and the straightest edge of the chip downagainst the cover glass. Next, place a chip fromthe suspect's car into the drop of permount,oriented in the same manner and with one edgetouching the first chip. Be sure there are no bubblesbetween the chips of paint and the cover glass. Itis best to mount the chips under the stereoscopicmicroscope. Tiny chips can be handled with dis-secting needles made sticky with the natural oilfrom the face. Allow the permount to dry; thenaffix another piece of slide of the same length tothe cover glass with the ground edge toward themounted chips and against them. Allow the prep-aration to dry enough so that it can be turned oveiand affixed to a whole microscope slide withpermount. When viewed with a microscope, bothchips will be visible and the layer structure, layersequence, color and inclusions can be compared.This method of mounting is for very tiny chips;larger chips could be broken so that portions couldbe mounted in the manner described. It has notbeen necessary to grind or polish the edges ofpaint chips in order to make detailed comparisons;'in fact the texture left by the fracture reveals othercharacteristics for comparison. Larger chips ofpaint lend themselves to other methods of exami-nation, - but when only a few tiny pieces arerecovered, examination is often limited to themicroscope. As the number of layers increases, thevalue of the comparison as evidence also increases,and a tiny chip of paint scarcely visible to thenaked eye might have ten layers of paint; thisevidence properly presented would weigh heavilyin court despite the size.If enough chips of paint are recovered from thevictim, micro-chemical examinations may be con-ducted. The reaction of the paint chips to a seriesof organic solvents and corrosive acid and alkalisolutions may be observed through a microscope.Slides with a series of wells on them are suitablefor this type of examination. Solubility and pro-gressive color changes may be compared by usingthe same kinds of solutions to treat both the chipsof paint from the victim and chips of paint fromthe suspect's car. Spectrographic and X-ray dif-fraction examinations may be conducted if enoughmaterial is available.Differences in the chemistry of the tiny paintchips may be revealed by the use of a series offilters during microscopic examination and com-parison. These filters can be placed one at a timeI BREWER, JAmEs G. AND BURD, DAVID Q., PaintComparison, Tim JOURNAL OF CRIMINAL LAW ANDCRIMINOLOGY Vol. 40 No. 2, Page 230, July-Aug. 1949.2 VILLIAMS, JOI.I, Examination of Paint Chips andScrapings. JOrRNAL oF CRIMINAL LAW, CRIMINOLOGYAND POLICE SCIENCE, Vol. 44, No. 5, Jan.-Feb., 1954.[N7ol. soPHYSICAL EVIDENCE IN HIT AND RUN ACCIDENTSFigure 4Tiny piece of tissue recovered from suspect's car.between the light source and the chips of paintbeing compared. The series of filters should varyfrom the deep red end of the spectrum throughthe various colors to the violet end of the spectrum.Paint samples of different composition which lookalike in color and hue with daylight usually can bedetected by such an examination.Visual examination of the tiny paint chips whichhave been mounted for microscopic study may bemade for fluorescence -when an ultraviolet sourceof light is used; visible light should be excludedwhen such an examination is made. Photomicro-graphs may be made using both an ultravioletsource and an infrared source. When makingphotographs on infrared film, a Wratten #87filter will exclude light of shorter wave length thaninfrared; this filter should be placed between theobjective lens and the paint chips being examinedor between the film and the optical system.Sometimes examination of the body will revealmarks which have been caused by the force of thebody striking against the contours of the vehicle,decorative strips, insignia, or structural featureswhich may indicate the make of the vehicle. If thevictim lives, the marks will become darker withthe passage of time and the outline blurred; if thevictim died quickly, the bruise or extravasationwill become more apparent after the embalmingprocess is completed-formalin causes the blood tobecome dark brown.Imprints of the cloth pattern of clothing wornby the victim may be observed in the paint or thechrome surfaces and the greasy portions of theundercarriage of the suspected vehicle. When ther,aint surface is marred with a sliding impactagainst the victim, a transfer of the paint to theclothing occurs. Visible smears of paint may beFigure 5Microscopic view of the tissue in figure 4. Note thefibers enmeshed in the tissue. The fibers came from thevictim's wool shirt which was dark blue in color.found on the clothing of the victim. Sometimesthese smears, when examined with a microscope,will reveal traces of the lower layers of paint as wellas the top layer; a microscopic examination of thesmears should be made before concluding the colorof the suspect's car by gross examination.During the examination of the suspect's cardetailed notes should be taken and photographsmade of all damage to the vehicle. Careful obser-vation should be made of all areas which have beerwiped clean of road film and dust. Technical ex-perts should be called to make a search of thevehicle for human blood stains, human hairthreads and fibers, and tissue fragments. Prelimi-nary tests for identification of blood such asbenzidine reagent should not be relied on in theseexaminations because of the usual presence ofsmashed insects which may give positive reactionto these reagents. Too little effort is usually expended in the search for biological traces otherthan blood on the suspected vehicles.Tiny pieces of tissue which are just visible to thenaked eye may reveal with microscopic andserologic examination information unexpected byCHARLES A. DAVISthe investigator (figure 4). Normal saline extractsof the bits of tissue when treated with anti-humanprecipitin serum may reveal the human origin.Microscopic examination of the gross specimenmay also reveal fibers which can be compared withfibers from the victim's clothing (figure 5); acomparison of the dye with which the fibers havebeen colored can be conducted by the methoddescribed for paint chips in which a series offilters is used. After extraction of the tissue withnormal saline, the tissue may be fixed, dehydrated,embedded in paraffin and sectioned on a microtomewith routine microtechnique. A study of the slidesprepared in this manner will reveal the kind oftissue (i.e. skeletal muscle, cutaneous, brain, etc.).Even when the tissue has been dehydrated priorto discovery, fixation following extraction innormal saline and routine microtechnique endingwith histologic staining of the slides usually revealsnuclei and cytoplasmic detail. Testimony in courtof the finding and identification of a piece ofhuman skeletal muscle or other tissue makes veryimportant evidence in the prosecution of suspectedhit and run drivers.Another important trace material which is over-looked on suspected vehicles is fluid fat. When avictim sustains a compound fracture or deeplaceration, fluid fat frequently escapes from thewound. Vehicles with abundant traces of fluid faton them have been observed when blood traceswere minute. The reason fluid fat is overlooked byinvestigators is because it appears to be splashstains of dirty water. Since fat or oil does not dry.every particle of dust which comes into contactwith it adheres to it, and by the time the investi-gator can examine the vehicle, the fat is so coatedwith dust that it does, indeed, resemble splashes ofmuddy water. Particles of "solid" fat may be foundon or near the bumper at the site of the initialimpact. Here again, careful serologic examinationof these fat stains will reveal the human origin ofthe material.[Vol. 50

Notes on Physical Evidence in Pedestrian Hit and Run Accidents

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Notes on Physical Evidence in Pedestrian Hit and Run Accidents

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