CRIME SCENE RECONSTRUCTION: FORENSIC BLOODSTAIN PATTERN ANALYSIS

1. Chapter 10 CRIME SCENE RECONSTRUCTION: FORENSIC BLOODSTAIN PATTERN ANALYSIS

2. 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 • Forward spatter • High velocity spatter • Impact spatter • Low velocity spatter • Medium velocity spatter • Parent drop • Satellite spatter • Spine • Skeletonization • Transfer pattern • void

3. 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.

4. Bloodstain Pattern Analysis (BPA) What can an investigator learn from the analysis of a blood spatter? • Type & velocity of weapon • # of blows • Handedness of assailant (right or left-handed) • Position & movements of the victim and assailant during and after the attack • Which wounds were inflicted first • Type of injuries • How long ago the crime was committed • Whether death was immediate or delayed Source: http://science.howstuffworks.com/bloodstain-pattern-analysis1.htm http://www.crimescenetwo.com/img/popup/book2p2.jpg

5. 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.

6. 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.

7. Height/Surface 0.5 0.5 1 1 2 2 3 3 Single drop of blood falling from various heights (m) onto various surfaces 13 smooth floor paper towel fabric

8. 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.

9. 16 Point of Convergence

10. Bloodstain Analysis

11. Stain Patterns of Blood • A shooting may leave a distinct gunshot spatter pattern. • 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

12. bullet exits foam Bullet enters foam bullet 59 Gunshot: back& forward spatter Bloodstained foam held just above target surface. Bullet passing L to R just above sheet Back-spatter on entry Forward spatter on exit

13. 61 Back spatter on steadying hand

14. 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

15. 51 Small arterial spurt spatter broken pottery

16. 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

17. 24 Downswing of Hammer

18. 25 Cast-off from Weapon ceiling

19. Tail of elongated stain points in direction of travel . Tail of wave cast-off points back to parent drop Parent drop wave cast-off 15 Wave Cast-off

20. 73 Trapped!

21. Impact Bloodstain • Low velocity (5 ft/s, 1.5 m/s; >3mm drop) • e.g. free-falling drops, cast off from weapon • Medium velocity (5-25 ft/s, 7.5 - 30 m/s; 1-3mm drop) • e.g. baseball bat blows • High velocity (100 ft/s, >30 m/s; < 1mm drop) • e.g. gunshot, machinery

22. 55 Medium velocity blood spatter.Point of impact 15 cm in front of vertical target surface 6” ruler

23. 80 90 10 60 50 40 70 20 30 Angle of Impact Gravitational dense zone at lower edge Adapted from Introduction to Forensic Sciences, W. Eckert, CRC, 1997

25. 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, footprints, footwear prints, tool prints, and fabric prints in blood.

26. 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.

27. 72 Flow pattern

28. 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. 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. Images from http://www.bloodspatter.com/BPATutorial.htm

29. 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. • HemaStix is a strip that has been coated with tetramethylbenzidine (TMB) and will produce a green or blue-green color with the presence of hemoglobin.

31. 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.