Blood Spatter Analysis General Info gained from bloodstain
Blood Spatter Analysis General Info gained from bloodstain pattern analysis: 1. the direction the blood originated from 2.the angle that the blood drop struck a surface 3. location/position of a bleeding individual at a
crime scene 4. min # of blows that struck a bleeding victim 5. approx location of a person delivering impact/ injury 6. movement of a bleeding person at the scene Activities to verify BSA
interpretation: Measuring and reconstruction Surface Tension and Surface Texture Blood is mostly water: has surface tension The harder / smoother / nonporous the surface, the less spatter there is (tile)
The rougher / more absorbent a surface is, the more spatter there is (carpet, wood, bed) The rougher surface breaks up the surface tension of the blood, which cause more spatter. Satellite spatter: small drops of blood
around the edges of a drop or pool of blood. Results from blood hitting a surface.s Notice spines 14
Angle of Impact 90 80
70 60 50 40
30 20 Gravitational dense zone at lower edge
Adapted from Introduction to Forensic Sciences, W. Eckert, CRC, 1997 10
Direction and Angle of Impact Shape of blood stain can help us tell direction of travel The more elliptical the shape, the greater the angle of impact, the longer the tail, the faster the blood was traveling. Angle of impact: angle formed between path of
bld drop and the surface it hits. FORMULA: sin A = width of blood stain length of bld stain + / - 5 degrees
IMPACT SPATTER Bld stain pattern produced when an object makes forceful contact with a source of blood Forward spatter: outward and away from the source of the bld Backward spatter: (blowback) backward from the source
Classification of impact spatter: based on the velocity of the blood droplet (speed) Force / velocity / increase / decrease Gunshot: back& forward spatter 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 59
Back spatter on steadying hand Classifying Impact Spatter LOW VELOCITY IMPACT SPATTER (LVIS) Drop moving less than 5 ft/sec
Diameter of drop is 3mm or more Dripping bld, cast off, splashing, arterial spurting MEDIUM VELOCITY IMPACT SPATTER (MVIS) Diameter of 1-3 mm Moving 5-25 ft/sec Blunt force truama
HIGH VELOCITY IMPACT SPATTER (HVIS) Diameter less than 1 mm, looks like a fine mist Moving 100 ft/sec or more Gunshots or explosions LVIS
MVIS HVIS 65
Forward spatter (closer view) Origin of Impact Patterns Origin of impact: where the blood came from; source / position of victim, weapon, etc Area of convergence: 2D place (on the ground) where the blood originated from
Determined by drawing straight lines thru the longitudinal axis of several blood stains. Area of origin: 3D place where blood came from Use angle of impact and area of convergence
Stringing Method 1. find area of convergence and angle of impact. 2. place pole/stand as an axis on the area of convergence. 3. attach string to end of droplet and use protractor to lift string to correct angle. Tie
string to pole/Stand, maintaining proper angle. 4. View area and attach all strings. Gunshot spatter Guns: forward and back spatter Very fine drops, mist-like spray
Drawback effect: when blood (back spatter) enters the barrel of a gun Cast off Bld covered object flings bld onto surface(s) Bloody fist
Repeated blows by weapon Infer type object: width of pattern, size of drops related to size of object bld came from Min #: each blow marked by upward (and downward arc pattern (or forward and backward)
At least 2 hits- 1 to break skin, 2nd to pick up bld 24 Downswing of Hammer 25
Cast-off from Weapon ceiling 26 Overhead swing with bloodied metal bar
27 Cast-off Pattern (1/2) 28
Cast off Pattern (2/2) 1 2 3
29 Cast off Pattern (2/2) ? Sequence 30
Cast off Pattern (2/2) ? Sequence 1 (4 spots) 2
(3 spots) 3 (2 spots) If weapon does not pick up more blood, spatter from subsequent backswings becomes progressively less.
In practice weapon picks up more blood with each successful blow. 31 Three overhead swings with hatchet Arterial Spray
Spatter pattern created from a main artery injury- usually carotid in neck Bld spurts with heart beat Knife wound, stabbing Direction: vertical arc shows movement, lg stain at end of pattern
53 Neck incisions Hesitation injuries Probe in carotid artery
Thyroid cartilage 50 Arterial Spurt Pattern Blood exiting body under arterial
pressure Large stains with downward flow on vertical surfaces wave-form of pulsatile flow may be apparent 52
Neck incisions (scene) 51 spatter Small arterial spurt
broken pottery 32 Cast-off & medium velocity spatter 33
Cast-off & medium velocity spatter 2 Expirated Blood Patterns Bld expelled from the mouth or nose, under great pressure; HVIS:very fine spatter
LVIS: drops seen as well See bubbles! (Also, can be lighter in color, mixes with saliva) Void Patterns Pattern created when an object / person blocks blood from hitting a surface
Important: bc it means something / someone is missing from the crime scene Contact / Transfer Patterns Transfer pattern: pattern when a bloody surface comes into contact with another surface.
Removed without movement Fingerprints, shoeprint, footwear, tool print, fabric all can leave transfer patterns SWIPE pattern: like transfer, but movement occurs; will feather
49 Blood pool (10 drops) after stamping Stamp 2 Transfer from hair
(hair-swipe) 1 69 Transfer from hair (hair-swipe) 2 70
Flow Flow patterns: patterns created by the movement of blood due to gravity Look for changes in flow pattern to see if body has been moved.
71 Flow Patterns Blood flows horizontally & vertically Altered by contours, obstacles Often ends in pool
72 Flow pattern 73 Trapped!
76 Blood flow on shirt Horizontally to R side
77 Pattern on shirt Pools Drying time is related to environmental conditions.
Skeletonization: the edges of a drop of bld will dry quickly- usually within 50 sec. The skeleton will remain even if the blood drop is wiped/swiped. Drip Trail Formed by bld dripping off an object
Can help determine speed and direction of moving object / person. The more circular the drops are, the slower the person was moving And look at the direction of the tails Documentation
PHOTOS, PHOTOS, PHOTOS! Whole scene for overall patterns and orientation Up-close- with something (like a ruler) for scale.
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