forensic science lab activity bloodstains passive transfer projected
TRANSCRIPT
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Forensic Science Lab Activity
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Bloodstains
PassiveTransfer
Projected
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• A transfer bloodstain is created when a wet, bloody surface comes in contact with another surface.
• Occasionally, a recognizable image of the original surface may be observed in the pattern, such as a hand or shoe pattern.
• Subdivided into Contact bleeding, Swipe or Smear, Wipe, and Smudge.
Transfer Bloodstain Patterns
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Dripped Spilled
Projected
patterns created by same volume of blood,from same source to target distance
Bloodstain Patterns
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• Projected bloodstains are created when a blood source is subjected to an action greater than the force of gravity.
• The size, shape, and number of resulting stains will depend on the amount of force utilized to strike the blood source.
Projected Bloodstain Patterns
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• Arterial Spurt / Gush - Bloodstain pattern from blood spurt under pressure from a cut artery.
• Cast-off Stains - Blood released or thrown from a blood-soaked object in motion.
• Impact Spatter - Blood stain patterns created when a blood source receives a blow or force resulting in the random dispersion of smaller drops of blood.
Arterial
Projected Bloodstain Patterns
Cast-Off
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Impact
• Low Velocity - Gravitational pull up to 5 feet/sec. Relatively large stains 4 mm and greater.
• Medium Velocity - Force of 5 to 25 feet/sec. Stain size 1 to 4 mm.
• High Velocity - Force of 100 feet/sec. and greater. Stain size 1 mm and smaller (Mist like appearance).
Low Medium High
Projected Bloodstain Patterns
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• DIRECTIONALITY OF BLOODSTAINS
• When a droplet of blood strikes a surface perpendicular (90 degrees) the resulting bloodstain will be circular.
• Blood that strikes a surface at an angle less than 90 degrees will be elongated or have a tear drop shape.
• Directionality is usually obvious as the pointed end of the bloodstain ( tail ) will always point in the direction of travel.
Projected Bloodstain Patterns
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IMPACT ANGLE DETERMINATION
• ANGLE of IMPACT is the acute angle formed between the direction of the blood drop and the plane of the surface it strikes
By utilizing trigonometric functions its possible to determine the impact angle for any given blood droplet.
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• SIN θ = Width (a) 1.5cm
Length (c) 3.0cm
What would the formula be?
Projected Bloodstain Patterns
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• POINT OF CONVERGENCE AND ORIGIN DETERMINATION
2 Dimensional Analysis
Projected Bloodstain Patterns
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• POINT OF CONVERGENCE AND ORIGIN DETERMINATION
3 Dimensional Analysis
Projected Bloodstain Patterns
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• POINT OF CONVERGENCE AND ORIGIN DETERMINATION
Projected Bloodstain Patterns
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Cast-off Pattern (1/2)Cast-off Pattern (1/2)
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Cast off Pattern (2/2) Cast off Pattern (2/2) ? Sequence? Sequence
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Three overhead swings with hatchet
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Cast-off & medium velocity spatter
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Cast-off & medium velocity spatter 2
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Cast-off Pattern ? ObjectCast-off Pattern ? Object
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Cast-off PatternCast-off Patternfrom Handfrom Hand
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Cast-off pattern from bloodied hand swung in front of target
6” ruler
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Drip PatternDrip Pattern
• Free-falling drops dripping into wet blood
• Large irregular central stain
• Small round & oval satellite stains
.. .......
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Drip 1:Drip 1:
Blood dripping into itself from height of 1 m (8 drops)
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Drip 2Drip 2
Blood dripping into itself from height of 1 m (8 drops)
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Dripping onto steps
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Splash PatternSplash Pattern
• Volume > 1 ml
– Subjected to LV impact
– Thrown
– Tipped
• Large central irregular area surrounded by elongated peripheral spatter pattern
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Splash 1Splash 1
5 ml blood squirted from a syringe from a height of 1 m
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Splash 2Splash 2
5 mL blood squirted from a syringe from a height of 1 m
43
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Splash 3Splash 3
5 mL blood squirted from a syringe from a height of 1 m
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Splash onto vertical surface
6” ruler
10 ml blood thrown 1 m onto a vertical target surface
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Stamping in blood 1
Area seen in close-up in next slide
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Stamping in blood Close-up of heel area
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Stamp 1Stamp 1
Blood pool (10 drops) before stamping
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Stamp 2Stamp 2
Blood pool (10 drops) after stamping
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Arterial Spurt PatternArterial Spurt Pattern
• Blood exiting body under arterial pressure
• Large stains with downward flow on vertical surfaces
• wave-form of pulsatile flow may be apparent
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Small arterial spurt
spatter
broken pottery
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Neck incisions (scene)
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Wipe PatternsWipe Patterns
• Object moves through a wet bloodstain• Feathered edge suggests direction
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Transfer PatternsTransfer Patterns
• Wet, bloodied object contacts a secondary surface
• Transfer from:
– hand, fingers
– shoes, weapon
– hair
• Transfer to:
– walls, ceilings
– clothing, bedding
• Produces mirror-image of bloodied object
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Transfer from hair (hair-swipe) 1
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Transfer from hair (hair-swipe) 2
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• 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.
Images from http://www.bloodspatter.com/BPATutorial.htm
Blood Spatter Movie
Review Types of Bloodstain Patterns