Chapter 10 CRIME SCENE RECONSTRUCTION FORENSIC BLOODSTAIN PATTERN
Chapter 10 CRIME SCENE RECONSTRUCTION: FORENSIC BLOODSTAIN PATTERN ANALYSIS
Vocabulary Terms • • • Angle of impact Area of convergence Area of origin Arterial spray Back spatter Cast-off Drip trail pattern Expirated blood pattern Flow pattern FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein • • • Forward spatter High velocity spatter Impact spatter Low velocity spatter Medium velocity spatter Parent drop Satellite spatter Spine Skeletonization Transfer pattern void © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 10 -2
Crime Scene Reconstruction • The method used to support a likely sequence of events by the observation and evaluation of physical evidence as well as statements made by those involved with incident. – Medical examiners – Criminalists – Law enforcement • All parties recover physical evidence and sort out the events surrounding the occurrence of a crime. FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 10 -3
Bloodstain Pattern Analysis (BPA) What can an investigator learn from the analysis of a blood spatter? ü Type & velocity of weapon ü # of blows ü Handedness of assailant (right or left-handed) ü Position & movements of the victim and assailant during and after the attack ü Which wounds were inflicted first ü Type of injuries ü How long ago the crime was committed ü Whether death was immediate or delayed Source: http: //science. howstuffworks. com/bloodstain-pattern-analysis 1. htm http: //www. crimescenetwo. com/img/popup/book 2 p 2. jpg FORENSIC SCIENCE: An Introduction, By Richard Saferstein 2 nd ed. © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 10 -4
Stain Patterns of Blood • CSI responsibilities: – location, distribution, and appearance of bloodstains and spatters may be useful for interpreting and reconstructing the events that produced the bleeding. • Surface texture and the stain’s shape, size, and location must be considered when determining the direction, dropping distance, and angle of impact of a bloodstain. FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 10 -5 5
Stain Patterns of Blood • Surface texture – In general, the harder and less porous the surface, the less spatter results • Wood vs. marble • Direction of travel of blood striking object – Pointed end of a bloodstain always faces its direction of travel • Impact angle of blood on a flat surface can be determined by measuring the degree of circular distortion – @ right angles the blood drop is circular – As the angle decreases, the stain becomes elongated. FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 10 -6 6
13 Single drop of blood falling from various heights (m) onto various surfaces 0. 5 1 1 Height/Surface 2 2 3 3 FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein smooth floor paper towel © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 fabric 10 -7
Lines of Convergence • Draw straight lines down the long axis of splatter & notice intersection • Origin Point – The intersection or point of convergence of the lines represents the origin point. FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 10 -8
16 Point of Convergence FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 10 -9
• Bloodstain Analysis FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 10 -10
Stain Patterns of Blood • A shooting may leave a distinct gunshot spattern. – Forward spatter from an exit wound – Back spatter from an entrance wound. • Amount of back spatter depends on – location of injury – size of the wound created – distance between the victim and the muzzle of the weapon FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 10 -1111
Gunshot: back& forward spatter 59 Bloodstained foam held just above target surface. Bullet passing L to R just above sheet bullet exits foam Bullet enters foam bullet Back-spatter on entry Forward spatter on exit FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 10 -12
61 Back spatter on steadying hand FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 10 -13
50 Arterial Spurt Pattern • Blood exiting body under arterial pressure • Large stains with downward flow on vertical surfaces • Wave-form of pulsating flow may be apparent FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 10 -14
51 spatter Small arterial spurt broken pottery FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 10 -15
Cast-off From Weapon • A cast-off pattern is created when a blood-covered object flings blood in an arc onto a nearby surface • First blow causes bleeding • Subsequent blows contaminate weapon with blood • Blood is cast-off tangentially to arc of upswing or backswing • Pattern & intensity depends on: – type of weapon – amount of blood adhering to weapon – length of arc FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 10 -16
24 Downswing of Hammer FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 10 -17
25 Cast-off from Weapon ceiling FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 10 -18
15 Wave Cast-off Tail of elongated stain points in direction of travel . Tail of wave cast-off points back to parent drop Parent drop wave cast-off FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 10 -19
73 Trapped! FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 10 -20
Impact Bloodstain • Low velocity (5 ft/s, 1. 5 m/s; >3 mm drop) – e. g. free-falling drops, cast off from weapon • Medium velocity (5 -25 ft/s, 7. 5 - 30 m/s; 1 -3 mm drop) – e. g. baseball bat blows • High velocity (100 ft/s, >30 m/s; < 1 mm drop) – e. g. gunshot, machinery FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 10 -21
55 Medium velocity blood spatter. Point of impact 15 cm in front of vertical target surface 6” ruler FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 10 -22
Angle of Impact 90 60 80 50 70 40 Gravitational dense zone at lower edge 30 Adapted from Introduction to Forensic Sciences, FORENSIC SCIENCE: W. Eckert, CRC, 1997 An Introduction, 2 nd ed. By Richard Saferstein 20 10 © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 10 -23
FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 10 -24
Stain Patterns of Blood • Expirated blood pattern – pattern created by blood that is expelled from the mouth or nose from an internal injury • Void – created when an object blocks the deposition of blood spatter onto a target surface or object. • When an object with blood on it touches one that does not have blood on it, this produces a contact or transfer pattern. – fingerprints, handprints, footwear prints, tool prints, and fabric prints in blood. FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 10 -2525
Stain Patterns of Blood • A pool of blood occurs when blood collects in a level (not sloped) and undisturbed place. • Flows – Patterns made by drops or large amounts of blood flowing by the pull of gravity • The edges of a stain will dry to the surface, producing a phenomenon called skeletonization. • Trail pattern – A series of drops that are separate from other patterns, formed by blood dripping off an object or injury. FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 10 -2626
72 Flow pattern FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 10 -27
Blood Spatter Movie Types of Bloodstain Patterns • • • Passive Bloodstains – Patterns created from the force of gravity – Drop, series of drops, flow patterns, blood pools, etc. Projected Bloodstains – Patterns that occur when a force is applied to the source of the blood – Includes low, medium, or high impact spatters, cast-off, arterial spurting, expiratory blood blown out of the nose, mouth, or wound. Transfer or Contact Bloodstains – These patterns are created when a wet, bloody object comes in contact with a target surface; may be used to identify an object or body part. – A wipe pattern is created from an object moving through a bloodstain, while a swipe pattern is created from an object leaving a bloodstain. FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Images from http: //www. bloodspatter. com/BPATutorial. htm 10 -28 Upper Saddle River, NJ 07458
How is Blood Evidence Detected? • UV lights to help find traces of blood & other bodily fluids that are not visible under normal lighting conditions. • Blood Reagent Tests (Presumptive tests) • Detects hemoglobin in the blood. – Phenolphthalein (Kastle-Meyer test) and produces a pink color when it reacts with hemoglobin. – Hema. Stix is a strip that has been coated with tetramethylbenzidine (TMB) and will produce a green or blue-green color with the presence of hemoglobin. FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 10 -29
FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 10 -30
Documenting Bloodstain Evidence • Investigators should – Note, study, and photograph each pattern and drop of blood – Accurately record the location of specific patterns – The investigator should create photographs and sketches of the overall pattern • Two common methods of documenting bloodstain patterns are the grid method and the perimeter ruler method. FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 10 -3131
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