Transcript Bloodstain Pattern Analysis

Bloodstain Pattern
Analysis
The use of physics, math &
common sense to interpret
bloodstain patterns within a
forensic setting
Discoverable from bloodstain
pattern interpretation:
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Activity at the scene
Number of blows
Position of victim and/or assailant
Death immediate or delayed
Weapon characteristics
Blood
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Fluid travels through a series of tubes in the
body (arteries, veins, capillaries, etc…)
Transports oxygen and nutrients to cells
Carries carbon dioxide and wastes away from
cells
Helps stabilize internal pH
Carries infection-fighting cells
Helps equalize temperature
What’s in Blood?
Plasma portion (50-60% of total volume)
• 91-92% water
• 7-8% proteins
• 1-2% ions, sugars, lipids, amino acids, hormones, vitamins
Cellular portion (40-50% of total volume)
• White blood cells
Neutrophils
Lymphocytes
Monocytes
Eosinophils
Basophils
• Red blood cells
• Platelets
History
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1894-Dr. Eduard Piotrowski, wrote earliest reference
to bloodstain pattern analysis
1939-Dr. Victor Balthazard, first to use physical
interpretation of stains
1955-Dr. Paul Kirk, recognized value of bloodstain
interpretation in scene reconstruction. Defense
witness in Dr. Sam Sheppard trial.
1971-Professor Herbert Leon MacDonell promoted
bloodstain pattern interpretation as a tool in modern
criminalstic labs
1983-The International Association of Bloodstain
Pattern Analysts
Basic Principles:
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A free falling drop forms a
sphere or ball
A spherical drop will
break
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when it strikes another
object
when acted upon by some
force
Surface Texture Affects
Spatter Shape
Spatter (NOT Splatter)
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is produced by blood being impacted by a
force
Spatter size is dependent upon velocity
Low velocity impact spatter
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5 feet per second
spatter 3 mm or greater in diameter
From blood dropping into blood; stepping into
blood
Medium velocity impact spatter
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5+ ft per sec to 25+ ft per sec
spatter 3 mm or less in diameter
blunt trauma or sharp trauma
confusion: flicking bloody finger, expiration
check clothing of suspect for spatter
High velocity impact spatter
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100+ feet per second
spatter 1 mm or less in diameter
droplets travel only 3-4 feet horizontally
gunshot trauma; airplane prop; power tools;
explosion
confusion: expiration, fly specks difficult to
see
Arterial Gushing
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Shape = heartbeat
Cast-Off Bloodstains
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blood cast from a moving object
occurs with the backstroke during repeated
blows or stabs not true spatter
spatter averages 6 mm diameter
blunt or stab (# of trails + 1= min # of blows)
axe or machete (# of trails = min # of blows)
Determining Location of Blood
Source
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Direction of Travel
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Angle of Impact
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Tail of spatter will point in the direction of travel
Vertical drop results in circular spatter
Acute angle results in elongated spatter
Measure blood spatter width and length, then
calculate the angle it struck the surface
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Width/length = sine impact angle
Use inverse sine fxn to calculate angle
Attach string lines to each of these spatters and
the lines converge at location of blood source
Transfer Pattern
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Produced by a wet, bloody surface contacting
a second surface that may result in a portion
of a recognizable image (e.g., knife transfer
pattern)
Void Pattern
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Produced when an object located between
the source of the blood and the surface being
spattered is removed
negative image of the object
Swipe and Wipe
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Swipe -- putting blood onto a surface
Wipe - removing blood from an existing stain
Direction of Travel - feathering always points
in the direction of travel
Flow pattern
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If there is movement after blood flow, you
can see it as a change in the pattern
Drying Time
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Drying begins at the periphery and proceeds inward
Drying time is affected by
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surface type
amount of blood present
climatic conditions
Skeletonization of Bloodstains
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partially dry stains leave a ring that outlines the original
spatter
the dryer the stain the less skeletonization shown
Clotting Time
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clotting time outside of the body ranges from
3 to 15 minutes
spattered clots indicate that time passed
between initial bleeding and later blows
coughing of clotted blood may indicate post
injury survival time of victim
Discoverable from bloodstain
pattern interpretation:
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Activity at the scene
Number of blows
Position of victim and/or assailant
Death immediate or delayed
Weapon characteristics