Forensic Science Lab Activity

Bloodstains

PassiveTransfer

Projected

• 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

Dripped Spilled

Projected

patterns created by same volume of blood,from same source to target distance

Bloodstain Patterns

• 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

• 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

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

• 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

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.

• SIN θ = Width  (a) 1.5cm

              Length (c) 3.0cm

What would the formula be?

Projected Bloodstain Patterns

• POINT OF CONVERGENCE AND ORIGIN DETERMINATION

2 Dimensional Analysis

Projected Bloodstain Patterns

• POINT OF CONVERGENCE AND ORIGIN DETERMINATION

3 Dimensional Analysis

Projected Bloodstain Patterns

• POINT OF CONVERGENCE AND ORIGIN DETERMINATION

Projected Bloodstain Patterns

Cast-off Pattern (1/2)Cast-off Pattern (1/2)

Cast off Pattern (2/2) Cast off Pattern (2/2) ? Sequence? Sequence

Three overhead swings with hatchet

Cast-off & medium velocity spatter

Cast-off & medium velocity spatter 2

Cast-off Pattern ? ObjectCast-off Pattern ? Object

Cast-off PatternCast-off Patternfrom Handfrom Hand

Cast-off pattern from bloodied hand swung in front of target

6” ruler

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..

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Drip PatternDrip Pattern

• Free-falling drops dripping into wet blood

• Large irregular central stain

• Small round & oval satellite stains

.. .......

Drip 1:Drip 1:

Blood dripping into itself from height of 1 m (8 drops)

Drip 2Drip 2

Blood dripping into itself from height of 1 m (8 drops)

Dripping onto steps

Splash PatternSplash Pattern

• Volume > 1 ml

– Subjected to LV impact

– Thrown

– Tipped

• Large central irregular area surrounded by elongated peripheral spatter pattern

Splash 1Splash 1

5 ml blood squirted from a syringe from a height of 1 m

Splash 2Splash 2

5 mL blood squirted from a syringe from a height of 1 m

43

Splash 3Splash 3

5 mL blood squirted from a syringe from a height of 1 m

Splash onto vertical surface

6” ruler

10 ml blood thrown 1 m onto a vertical target surface

Stamping in blood 1

Area seen in close-up in next slide

Stamping in blood Close-up of heel area

Stamp 1Stamp 1

Blood pool (10 drops) before stamping

Stamp 2Stamp 2

Blood pool (10 drops) after stamping

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

Small arterial spurt

spatter

broken pottery

Neck incisions (scene)

Wipe PatternsWipe Patterns

• Object moves through a wet bloodstain• Feathered edge suggests direction

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

Transfer from hair (hair-swipe) 1

Transfer from hair (hair-swipe) 2

• 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