706 Lecture 2 Physical Pattern Evidence.pdf

FOS 706 Physical & Biological Evidence Physical Pattern Evidence  Physical Pattern Evidence  PROFESSOR LINDA ROURKE  Class characteristics  identification Individual characteristics  individualization Patterns  reconstruction Saferstein, R. (2001). Criminalistics: An Introduction to Fore...

FOS 706 Physical & Biological Evidence Physical Pattern Evidence  Physical Pattern Evidence  PROFESSOR LINDA ROURKE  Class characteristics  identification Individual characteristics  individualization Patterns  reconstruction Saferstein, R. (2001). Criminalistics: An Introduction to Forensic Science, (7th ed). Upper Saddle River, NJ: Prentice Hall. http://www.factsfi nder.com/Fingerpri nt.jpg http://www.blo odspatter.com/B PATutorial.htm Physical Pattern Evidence Pattern examination is used to analyze:       Marijuana Torn Paper Broken Wood Plastic Or Glass Fingerprints Typewriting Shoeprints Bitemarks  Bullet B ll t L Land d And Groove Markings  Handwriting  Hair Physical Patterns In Identification    Morphological identification (based on structural features) = physical pattern recognition    compare known and questioned pattern used by everyone often unconsciously Identify marijuana, species of origin of hair; drugs from spectral patterns http://www.sisweb.co m/art/hp/cocain3.gif http://www.dea.gov/p ubs/abuse/7-pot.htm Physical Matching Physical Patterns In Individualization   Very important & the most widely used approach to individualizations. Three applications of physical patterns to individualizations:    physical matching comparison of markings general shape/form comparison Saferstein, R. (2001). Criminalistics: An Introduction to Forensic Science, (7th ed). Upper Saddle River, NJ: Prentice Hall.   Uniquely associate pieces of materials with articles from which they are thought to have been separated. Should always be considered prior to chemical analysis. 1 Direct Physical Matches      Physical fit = jigsaw fit May be possible depending on material and random separation process. Easier with fewer large pieces pieces. Produce definitive individualizations. Should never be attempted in the field compromises trace evidence and may damage mating surfaces Comparison of Markings Markings produced when 2 surfaces come in contact:  Imprints  Indentations I d t ti  Striations Indirect Physical Matches        ex. plastic bags formed from continuous strip; wood grain comparison Imprints        Indentations Attempt when no direct physical match is possible; i.e. when very smooth cut separates pieces; separating surface is featureless; material is soft/elastic or deforms easily. Utilize surface and internal characteristics of separated pieces  continuity of patterns of surface markings, inhomogeneities, other internal features. 2-D contact marks Transfer of material to some surface Sometimes removal of material from surface Use photographic documentation Best to collect actual imprint when possible Examples: typewriting, fingerprints; footprints, shoe prints, palm prints, tire prints, fabric pattern imprints, lip prints Examine in lab by comparing questioned mark to exemplar produced by known object suspected of leaving mark  side by side or transparency overlay comparison. Striations 3-D contact patterns Produced when a harder material leaves an impression of its surface features and contours in a softer one No need for a transfer of matter Examples: breechbreech-face marking on head of a cartridge case, firing pin indentations, certain pry marks, footprints in soft mud/soil, plastic fingerprint impressions, teeth impressions, certain fabric impressions.      http://www1.istockphoto.com/fil e_thumbview_approve/115303/ 2/istockphoto_115303_bloody_fi nger_print.jpg http://www.fir earmsid.com/A _BulletID.htm produced by a dynamic process - sliding contact patterns degree of individualization depends on number and type of features present in mark and relationship of mark to case bullet striations are individualizable to a g gun wires drawn from same die have same marks but so much wire drawn through that there is no guarantee wire came from same spool bite marks in cheese or fruit; compare striations using a comparison microscope http://www.ballisticsexperts.com/News/AFTE%20Pu erto%20Rico/AFTE%20Puerto% 20Rico.htm 2 DOCUMENTATION, COLLECTION, AND PRESERVATION OF PATTERN EVIDENCE General Form Comparisons  These individuations are subjective in nature:      hair comparisons facial recognition when face is familiar handwriting comparison done by documents examiner dental xx-rays voiceprint comparisons DOCUMENTATION, COLLECTION, AND PRESERVATION OF PATTERN EVIDENCE Documentation  Long & medium range photographs: record general location & orientation, position relative to other evidence and landmarks  Close Close--up photos record detail, size, shape, any irregularities (use a scale); camera should be parallel to pattern plane to avoid distortions; use tripod; oblique lighting for indentation--type marks. indentation Documentation  Notes, sketches, and photography.  Documentation of pattern evidence should be thorough and precede any collection or preservation; record type, shape, directionality, measurements.. measurements Collection and Preservation    Physical Pattern Evidence      Fingerprints Bloodspatter Analysis Firearms & Toolmarks evidence Glass Reconstruction Footwear Imprints & Impressions Lifting Of Imprint Patterns - photography & written documentation; best to collect imprint if surface is amenable to this  best to make comparison with original instead of photo; lift imprint using commercial imprint lifting film; examine class and individualizing characteristics. Casting Materials - plaster of paris (hydrated calcium sulfate); use dental plaster for size comparisons since it has lower expansion factor; silicone rubber, moulage moulage,, wax, modeling clay, thermoplastic materials, synthetic resins can be used for fine detail 33-D pattern reproductions Special Casting Conditions - in snow, cast with sulfur (evolves less heat and hardens immediately); SnowSnowPrint--Wax can be used to coat/harden pattern prior to Print casting. Footwear & Tire Patterns  Tracks & trails: patterns for comparison and individualization. 3 Tire Tracks Variety of tread patterns Tire Tracks  Three main parameters for classification:    Wheelbase – distance between the front and rear axles of a vehicle Front & Rear Track widths – the length of an axle; the distance between centerlines of tread imprints on the ground. Careful measurement can identify manufacturer of vehicle involved. Kirk, P.L. (1974). Crime Investigation, 2nd Edition, Malabar, FL: Krieger Publishing Company. Footwear Patterns  Footwear Outsole Patterns from Shoewear   Impression prints in soft material such as mud, sand, mortar, snow, etc. Residue prints on solid surfaces by dust dust, blood, etc. Footwear Patterns   Document with photography Importance of having a scale in the photo! Electrostatic Lifting       For shoeprints in dust: DRY dust impressions Operate by charging a lifting film which has been placed over a surface bearing a dust print impression. During operation, the electrostatically charged lifting film is drawn down to the surface, and the dust particles in the impression are attracted to the lifting film film. The lifting film stores the electrostatic charge and thus retains the dust particles. Viewed with oblique light source. Use on linoleum tile, paper, seat covers, wood Bodziak, W.J. (2000). Footwear Impression Evidence: Detection, Recovery, and Examination, 2nd Edition. Boca Raton, FL: CRC Press LLC. 4 Electrostatic Lifting http://www.planetscience.com/whodunit/imageLibrary/jpeg164/237.jpg Bodziak, W.J. (2000). Footwear Impression Evidence: Detection, Recovery, and Examination, 2nd Edition. Boca Raton, FL: CRC Press LLC. Casting of Shoeprints  Casting material:     Plaster of paris (hydrated (hydrated calcium sulfate) or dental stone (preferred) Wire mesh for strength Use dental plaster for size comparisons since it has lower expansion factor Care so as not to destroy detail while casting. Impressions in Snow Difficulties:  Photography: low contrast imaging  Casting: casting materials may melt the snow, destroy details Impressions in Snow Acceptable Techniques:  Highlighting with colored aerosol sprays.  Combination of Snowprint Wax with dental stone. t  Sulfur Casting techniques. http://www.eplover.com /police_crimestopper.ht m Impressions in Snow Highlighting with colored aerosol sprays  easier to capture details photographically   Snow print wax is colored red G Gray auto t body b d primer i 5 Impressions in Snow Combination of Snowprint Wax with dental stone.  Aerosol spray coats & hardens the impression. impression  Protects the impression details during casting with dental stone. Bodziak, W.J. (2000). Footwear Impression Evidence: Detection, Recovery, and Examination, 2nd Edition. Boca Raton, FL: CRC Press LLC. Impressions in Snow Bodziak, W.J. (2000). Footwear Impression Evidence: Detection, Recovery, and Examination, 2nd Edition. Boca Raton, FL: CRC Press LLC. Sulfur Casting technique  Use crystalline sulfur, melted to just above melting point.  Evolves less heat and hardens/recrystallizes hardens/ recrystallizes immediately.  Pour over impression, capturing the impression details details..  Success depends on environmental conditions. Footwear Outsole Databases    Allows identification of footwear type. Computerized databases of known outsole patterns. M Manufacturer, f t model, d l size, i d dates t off production. Bodziak, W.J. (2000). Footwear Impression Evidence: Detection, Recovery, and Examination, 2nd Edition. Boca Raton, FL: CRC Press LLC. 6 Exemplar Preparation  Instead of comparing the suspect shoe to the evidence print, prepare a print from the suspect shoe for comparison Exemplar Preparation Imprint methods  Inked Prints  Oil/Black Powder Prints  Roller Transport Cleaner Film with Magnetic Powder/Black Toner Exemplar Preparation Inked Prints  Apply a thin coat of ink to the outsole.  Step the shoe onto paper “as if walking”.  Successively step onto paper substrates. substrates  Successive substrate can capture fine detail. Exemplar Preparation   Oil/Black Powder Prints Roller Transport Cleaner Film with Magnetic Powder/Black Toner Both use powder to capture print details. Comparisons   Compare cast of evidence imprint/impression to details of suspect shoe. Compare photograph of evidence print or lifted evidence print to a prepared exemplar print. Comparisons Footwear imprints/impressions  Class characteristics:       Length, Width, Overall Dimensions Shape Pattern Designs Distances Between Patterns Angles Flaws (Manufacturing) 7 Comparisons Tire track imprints/impressions  Class characteristics:    Zigzag pattern, number & dimensions N b off zigzags Number i per unit it llength th Degree of zigzag angle Kirk, P.L. (1974). Crime Investigation, 2nd Edition, Malabar, FL: Krieger Publishing Company. Comparisons Individualizing Characteristics  Wear patterns  Irregularities  Damage, cuts  Accidental or intentional marks Comparisons Considerations:  Class & individual characteristics  Positive and negative images  Continued wear of shoe subsequent to incident of concern. LABORATORY EXAMINATION OF PHYSICAL PATTERN EVIDENCE     Physical matching is easiest  compare point by point. Look for class and individualizing characteristics. Take into account cast shrinkage, movement when pattern was left, additional wear and tear of object which originally left pattern. Must use appropriate controls . De Forest, P.R., Gaensslen, R.E., & Lee, H.C. (1983). Forensic Science: An Introduction to Criminalistics, New York: MacGraw-Hill. 8 PHYSICAL PATTERNS IN RECONSTRUCTION Physical Pattern Evidence: Bloodspatter Blood Droplet Dynamics Falling, Projected, and Impacting Blood Droplets  Limited studies on dynamics of blood drops as projectiles p j & falling g bodies; focus on p patterns of blood drops as they impact on a surface.  Reconstructing a crime: scientist should perform tests under the same conditions, or as similar as possible, to the case situation    Reconstructions from Bloodstain Patterns Bloodstain Pattern Evidence Versus Serology Bloodstain patterns can be valuable in reconstructing a crime scene; in some instances this type of evidence will be more helpful than a serological analysis. Blood Droplet Dynamics Small falling drops have a spherical shape shape;; larger drops appear squatter & more flattened due to oscillations & air resistance http://www.ap.stmarys.ca/~smitchel/for201labs /blood_angle/blood_drop_tension.jpg Blood Droplet Dynamics Interpretation of Individual Droplet Stain Patterns Terminal velocity: velocity:  the acceleration is offset by air resistance  for average size blood drop from dripping, (0.05 mL), the terminal velocity is ~25 25 ft/sec attained after a 15 ft fall  smaller drops, the terminal velocity is lower and attained after falling a shorter distance Individual droplet patterns can give info on 1. approximate droplet speed at the time of impact 2 indication 2. i di ti off th the di direction ti off ttravell 3. indication of the forces or actions which produced the pattern 9 Pattern Characteristics Drop impacting normal to surface produces approximately circular, relatively symmetrical pattern Pattern Characteristics  Size of the pattern and its edge configuration affected by       original droplet size surface texture surface resilience surface porosity/absorbency speed at moment of impact; not necessarily height of the fall angle of incidence http://www.bloodspatter.com/BPATutorial.htm Speed   Higher velocities and rougher surfaces produce more ragged edges Satellite droplets sometimes ejected, fall outside the main stain area Speed     Angle of Incidence  normal impacts onto hard, smooth surfaces produce very circular spots with smooth edges droplets striking resilient surfaces have lower impact p and may y leave a smaller spot p p pattern absorbent surfaces can diffuse the droplet to produce a larger stain should test on the surface in question Angle of Incidence This angle is measured with respect to the normal to the surface as opposed to the angle of impact which is measured with respect to the plane of the surface itself Angle of Incidence + Angle of Impact = 90° Angle of Impact 10 Angle of Incidence   Angle of Incidence Blood projected away from the surface as a result of complex wave motions set up in the drop at impact may travel further and land ahead of the main pattern The more oblique the angle, the more elongated is the stain. Angle of Incidence angle of incidence =  cos   d minor diameter  D major diameter Production of Blood Droplets      arccos d D Types of Bloodstain Patterns Different forces/activities produce different kinds of bloodstain patterns:  Radial Spatter p Patterns from Blows: a weapon striking pooled blood from repeated blows emanates in a radial pattern; missing sector indicates position of assailant  Droplets allowed to form slowly have an average volume ~0.05 mL - typical of dripping blood. Actual volume depends on object from which the blood is dripping dripping. More rapid formation with high energy interactions produce smaller droplets, i.e. from a shooting or an explosion. Should form an opinion from the overall pattern, not just a few isolated spots. http://www.bloo dspatter.com/BP ATutorial.htm Types of Bloodstain Patterns  Arc Patterns from a Swinging Weapon: swinging a bloodblood-covered weapon (pipe, bat); blood impacts a surface f (ceiling, ( ili wallll or furniture); can define the plane of the arc of weapon swing and position of assailant; may also indicate handedness of assailant http://www.bloodspatter.c om/bloodspatter.pdf http://www.bloodspatter.com/BPATutorial.htm 11 Types of Bloodstain Patterns  Patterns from Artery Spurts which spurt blood in rhythm with the pulsating contractions of the heart; pressure/force will level off as more blood is lost; moving victims can leave a distinct pattern Types of Bloodstain Patterns   Trail Patterns: crimes of violence and burglaries; trail from wound or from a dripping weapon; aid in reconstruction Flow Patterns and Pools: p post--mortem events, post disturbance or moving of the body; degree of clotting also important; volume of bloodshed compared to expected blood volume to determine if scene is secondary scene http://www.bloodspatter.com/BPATutorial.htm Types of Bloodstain Patterns  Contact Patterns and Transfers: reveal class or individual characteristics (fingerprints, footprints, fabric imprints); reconstruction aid Types of Bloodstain Patterns  Blood Patterns from Shooting     perforating wounds wounds:: blood droplets of various size + tissue expelled from exit wound travel in a conical pattern in general direction of bullet; small amount of back spatter possible penetrating wounds will have no forward spatter droplet size range may vary from large to minute (mist--like) (mist very fine droplets do not travel far http://www.bloodspatter.com/BPATutorial.htm http://www.fbi.gov/publications/leb/2005/feb2005/feb2005.htm Preserving And Interpreting Bloodstain Patterns   Reconstruction of geometric and spatial relationships between people and objects can often be determined but require careful documentation documentation. Any reconstruction hypothesis must take into account all the facts and observations available. 12