Crime Scene Processing Series

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• Crime Scene Processing Series
• INTRODUCTION TOBASIC BLOODSTAIN PATTERN
  RECOGNITION
• New Mexico State Police
• Criminal Investigation Section
• Crime Scene Team

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BLOODSTAIN CATEGORIES

• There are 4 basic categories of bloodstain
  patterns
• Transfer stains
• Wipes, Swipes (smearing of bloodstains)
• Pattern Transfers
• Passive stains
• Blood Drops, Flows, Pools
• Projected or impact stains
• Spatter, Cast-off Stains
• Miscellaneous Stains
• Fly spots, expiratory blood, voids

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TRANSFER STAINS
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Wipes (object moving through a preexisting stain)
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Swipes(blood transferred onto a surface by
another moving object)
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HAIR SWIPE
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TRANSFER PATTERN

• The pattern created when a wet bloody object
  comes in contact with another surface, leaving a
  pattern, which may identify the first object.

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TRANSFER PATTERN
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BLOODY SHOE PRINT
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PATTERN TRANSFER
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PASSIVE AND PROJECTED STAINS
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THESE STAINS ARE ALSO CATEGORIZED BY VELOCITY

• There are three categories that refer to the
  velocity of the wounding agent that comes into
  contact with the blood or blood source
• Low velocity
• Medium velocity
• High velocity
• It is not the speed that the blood flies through
  the air

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PASSIVESTAINS
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PASSIVE STAINS

• Gravity is the only force acting on the blood or
  the blood source (whatever is bleeding).
• These stains would be categorized as LOW VELOCITY
  stains.

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LOW VELOCITY

• Force only from gravitational pull (free falling
  or flow)
• Most drops in the pattern are 3 mm in diameter or
  larger
• Remember when looking at the size of a drop,
  look at the average size of the all drops in the
  pattern.
• Patterns may have individual drops that fit the
  other categories.

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DROPS
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PASSIVE FLOW
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POOLS (blood in blood)
Serum separation
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PROJECTED STAINS

• TERMINOLOGY

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DIRECTION

• The direction a given droplet was traveling at
  the time it impacted a surface.

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ANGLE

• The angle of impact (bloodstain)

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ORIGIN

• The general area in space where the drop
  originates in regard to its flight path

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ORIGIN
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IMPACT SITEpoint on the body that receives the
force of a blow (impacts number of blows)
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MEDIUM VELOCITY SPATTER

• Most medium velocity spatter stains usually range
  from 1 mm to 4 mm in diameter.
• Spatter stains may travel great distances from
  the source
• Often seen in beatings, stabbings or cast-off
  stains

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IMPACT SPATTER(MEDIUM VELOCITY)
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FORWARD SPATTER

• Bloodstains projected in the same direction as
  the force or energy being applied.
• Seen in both medium velocity and high velocity
  events.

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MEDIUM VELOCITY SPATTER
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Forward Spatter
Overhead (aerial) view
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A closer look
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A BETTER VIEW OF AVERAGE MEDIUM VELOCITY STAIN
SIZE
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CAST-OFF STAINScreated when blood is flung or
projected from an object in motion, or one that
suddenly stops its motion
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AN EXAMPLE OF CASTOFF
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CASTOFF STAINS
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MORE CASTOFF STAINS
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HIGH VELOCITY

• Most spatter stains are atomized (1 mm or less)
  and can appear as a mist
• May travel at most 3 to 4 feet, but can travel
  further.
• Can be created by firearms, explosions, high
  speed machinery.
• Expectorate stains can look like high velocity
  stains as well.

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HIGH VELOCITY
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EXAMPLE OF HIGH VELOCITY AND FORWARD-SPATTER
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BACK-SPATTER

• Bloodstains which are projected towards the item
  creating the force or energy. Most often found in
  gunshot situations.

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BACK-SPATTER
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BACK-SPATTER ON GUN
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DRAWBACK EFFECT

• The process of blood entering the barrel of a gun
  following the discharge of the weapon.
• This effect occurs when the gun barrel is very
  close to the body or touching the body.

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EXAMPLE OF DRAWBACK
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DRAWBACK
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MISCELLANEOUS STAINS
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VOIDS

• A pattern that is created when an object is
  between the blood source and the surface where
  the blood is striking.
• Voids show the specific location of objects at
  the scene.

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VOID
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FLY SPOTS

• Often confused with high velocity spatter.
• Flies within the scene will feed on blood found
  there. This blood is both tracked about and
  regurgitated by the flies.
• The marks are extremely small but a pattern may
  be evident.

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FLY SPOTS
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EXPIRATORY BLOOD

• Look for air bubbles (or bubble rings) in the
  bloodstains.
• Expiratory blood often looks like high velocity
  bloodstains.
• Often chemical tests for saliva determine if the
  bloodstain is expiratory or high velocity.

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Expiratory Blood
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QUESTIONS?
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CREDITS

• Bevel, Tom and Gardener, Ross, Bloodstain Pattern
  Analysis, Second Ed., CRC Press (2002)
• Lee, Henry, Physical Evidence, Magnani
  McCormick Inc. (1997)
• Taylor, David, et al., Death and Homicide
  Investigation, Specialized Law Enforcement
  Training, Inc. (2002)