Blood Spatter Analysis

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Blood Spatter Analysis

• compiled by Prof. John MooreParkland
  CollegeChampaign, IL

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• I see no more than you, but I have trained
  myself to notice what I see.
• Sherlock Holmes, The Adventure of the
  Blanched Soldier

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How did it get there?????

• passive
• projected
• (or void of projected blood)
• transfer

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The standard questions..

• Is it blood?
• Is it human blood?
• Who is the owner of the blood?

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The new question..

• Can the blood stain or blood stains give
  additional information about the mechanism by
  which the blood reached the target surface?
• Location
• Time sequencing
• Number of wounds/blows
• Other individuals present

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1.) Blood spatter analysis

• Blood should generally stay inside of a person.
• Finding blood at the crime scene is most likely
  an indication that something has happened to
  someone!
• Among other things, the investigators must
  determine
• a) is the fluid truly blood?
• b) is it human blood?
• c) can the blood be identified as coming from a
  specific person? (Note - crimes at slaughter
  houses really prove difficult to analyze.)

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Blood spatter analysis cont.

• Blood is found at the scene of many violent
  crimes. However, violence can occur without
  blood loss, and the presence of blood does NOT
  have to indicate the commission of a crime.
• It can be matched to a suspect with a high
  degree of accuracy.
• The pattern of blood stains spatter can tell
  much about exactly what happened at the scene.

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Blood spatter analysis cont.

• As an example of how blood is left at a scene,
  consider a scenario where someone cuts their hand
  while at a crime scene. In most cases they will
• Grab it (the cut hand)
• Sling it (out of reaction to the pain)
• Run it under water (because that is what we have
  been told to do since childhood)

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Grab it

• This will deposit blood onto the hand used to
  grab the injured hand.
• In all likelihood, at some point in time blood
  will be transferred to some environmental
  surface at the crime scene by this blood covered
  hand.
• Grabbing it will generally not stop the bleeding
  so dripping will occur.

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Sling it

• Slinging the blood will leave a pattern on nearby
  environmental surfaces.
• Such patterns can also originate from blood being
  slung from a moving knife or impact weapon.

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Run it under water

• Running water over an bleeding injury tends to
  disperse the blood to a larger area if done
  outside of a sink, e.g., using a hose in the
  backyard.
• Running the water over the bleeding injury in a
  sink will usually leave detectable blood evidence
  in the sink, or the trap system of the sink.

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Blood components

• Blood is comprised of both CELLULAR and LIQUID
  components.
• The cellular elements and the liquid component of
  blood are normally mixed with the formed
  cellular elements floating in the liquid phase.
  (The diagram shows the two phases separated.)

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Blood separated into cellular liquid
components
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Blood characteristics

• Average person has between 5-6 liters of blood
• Blood is approximately 6x thicker than water -
  like a thin syrup.
• Blood can both dry as well as clot. Both
  versions will often be seen at a crime scene.

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BLOOD CLOTTING

• Blood clotting is NOT the same as blood drying.
• Drying is a function of losing water.
• Clotting is an active biological process where
  the liquid portion of the blood (plasma) changes
  to a gel-like substance.
• Blood generally clots in 3 13 minutes, with 7
  minutes being a good average.

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Falling blood drops

• The SHAPE of a free-falling drop of blood is
  roughly SPHERICAL. Note that this is unlike the
  classic Atear-drop_at_ shape often seen!
• The blood drop will oscillate as it falls due to
  air resistance.

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Blood drop origination
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passive or gravity drop
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Blood drop oscillation
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• Corona effect D/t blood falling into a
  pre-existing pool of blood. The pattern radiates
  out from the pint of impact. (When stopped via
  flash photgraphy, the radiating droplets look
  like a crown, hence the term corona.)
• See following slide for images of corona effect.

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Stain smooth surface
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Stain textured surface
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Stain rough, textured surface
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stringing
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BLOODSTAIN SIZE - The bloodstain produced by a
blood drop is PROPORTIONATE TO THE SIZE OF THE
DROP.
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Blood drop impact
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Blood spatter

• A BLOOD SPATTER is the result of an impacting
  FORCE striking a STATIC pool of blood. NOTE -
  This is NOT called blood SPLATTER! (Another way
  to think of this is that splatter is the sound
  made when the blood is caused to spatter.)
• See following slide for mechanism of spatter.

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Blood spatter mechanism of formation
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Blood spatter mechanism of formation
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Splash pattern
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Cast-off
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Blood spatter Application to crime scene
evidence.

• The SPHERICAL drop of blood (regardless of
  source) will impact some physical structure, thus
  causing a BLOODSTAIN. If the drop strikes
  PERPENDICULAR to the surface involved, the WIDTH
  and LENGTH of the bloodstain will be equal, for
  all intents purposes. If the drop is moving
  horizontally, or if the surface is not
  perpendicular to the path of the drop, the
  bloodstain will take on an elliptical or oval
  shape.

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Things that can be determined from blood stain
pattern analysis

• What occurred at the scene.
• Who was (or was NOT) present.
• How many blows were struck.
• Position of victim and assailant.
• Origin of the bloodstains.
• Sequence of events.

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Blood spatter cont.

• When seen from above, a stain can sometimes
  resemble a tadpole or exclamation point! The
  dot of the exclamation point indicates the
  DIRECTION OF TRAVEL of the blood drop.
•  
• Some drops dont taper as much (d/t different
  types of surface that they impact, or different
  impact angles) - and will become more jagged in
  appearance. This jagged edge is the direction of
  travel.
• The shape of the stain can also help determine
  the angle at which the blood impacted the
  surface.

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angle of impact vs. stain shape
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angle of impact vs. stain shape
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angle of impact vs. stain shape
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angle of impact vs. stain shape
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angle of impact vs. stain shape
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Spatter size

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• Spatters are often lumped into categories such as
  low, medium, and high velocity spatters
  (LVS/MVS/HVS). There is, unfortunately, a
  tremendous amount of variability overlap. Due
  to this - pattern analysis CANNOT BE BASED UPON
  AN INDIVIDUAL STAIN. The MAJORITY OR
  PREPONDERANCE OF STAINS must be used as the basis
  of an evaluation.

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LVS characteristics

• Usually associated with activities such as
• Drops falling passively to target
• Drip spatter (blood dripping into a pool of
  blood)
• Splashed blood
• Stepping into pool of blood
• Large volume of blood falling at least 4 inches
• LVS are usually large, d/t low applied force. (gt
  3mm)

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Low velocity
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MVS patterns

• Usually associated with
• Velocities of 5 25 fps
• Beatings or stabbings
• Most spatters are lt 3mm in diametrer

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Medium velocity
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HVS patterns

• Usually associated with
• Velocities in excess of 100 fps
• GSWs
• Explosions
• Mechanical accidents involving high speed
  machinery
• Majority of spatters are lt 1 mm (mist)

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HVS patterns cont.

• Dry quickly
• Do not travel far
• If GSW bullet entry angle detrmines spatter
  direction
• Often hidden (or missed) in textured surfaces,
  such as carpeting
• May exhibit both backspatter forward spatter

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Forward backspatter
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hvs
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High velocity
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Expiratory blood

• Expiratory blood can originated from two major
  locations the nose mouth, or from an open
  chest wound (commonly called a sucking chest
  wound in clinical settings.)
• If originating from the mouth, a degree of
  salivary dilution can occur, resulting in a blood
  stain that is noticeably lighter in appearance
  than one associated with normal blood.

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Expiratory Blood

• The arrow points to a stain cause by a
  bubble of expired blood hitting the target
  surface.

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Arterial gushing
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Arterial spurt
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Flow change d/t movement of body relative to
gravity
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transfer
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transfer
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transfer
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Transfer / sequencing
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transfer
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transfer
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Transfer / sequencing
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Uninterrupted swipe
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The following are some general rules of
bloodstain pattern analysis.
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• The smaller the size of bloodspatters, the
  greater the energy required to produce them. 
  Low, medium, and high velocity impact spatter may
  be identified by their respective sizes but
  exceptions must also one considered.
•  http//www.brazoria-county.com/sheriff/id/idtop.
  htm

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• Before a drop of blood can fall, absent any other
  form of applied energy, gravitational attraction
  acting on blood must exceed its surface tension.
•  http//www.brazoria-county.com/sheriff/id/idtop.
  htm

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• Diameter of a large bloodstain will be of little
  or not value in estimating the distance a drop of
  blood has fallen prior to impact.
•   http//www.brazoria-county.com/sheriff/id/idtop
  .htm

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• When considering the shape of a bloodstain for
  use in calculating its angle of impact, only a
  sharp, well-defined bloodstain should be used for
  measuring its width and length.
•  http//www.brazoria-county.com/sheriff/id/idtop.
  htm

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• Directionality of a blood drop while in flight is
  usually obvious from the geometry of its
  resulting bloodstain.  The pointed end indicates
  the direction of travel prior to impact on a
  surface.  Directionality may also be determined
  when edge scallops appear on only one side of a
  bloodstain.
•   http//www.brazoria-county.com/sheriff/id/idtop
  .htm

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• Correct interpretation of bloodstain patterns
  must include consideration of the surface texture
  of the material upon which the bloodstains have
  been deposited.
•  http//www.brazoria-county.com/sheriff/id/idtop.
  htm

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• Surface tension prevents spattering regardless of
  the distance a drop of blood has fallen before
  impacting a smooth, hard surface such as glass.
•   http//www.brazoria-county.com/sheriff/id/idtop
  .htm

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• Edge characteristics of a bloodstain have no
  value in establishing the distance a drop of
  blood may have fallen prior to impacting a
  surface unless the nature of the surface texture
  is considered.
•   http//www.brazoria-county.com/sheriff/id/idtop
  .htm

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• Conclusions as to the significance of a limited
  number of bloodstains should only be drawn with
  reservations and/or qualifications.  It should be
  remembered that a few bloodstains do not a
  pattern make.  There is nothing wrong with
  admitting that there are insufficient bloodstains
  available to form an opinion.   It is far better
  not to have an opinion than to have one that is
  incorrect.
•   http//www.brazoria-county.com/sheriff/id/idtop
  .htm

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• When a dozen or more small bloodstains are
  present in a recognizable pattern, their size may
  allow a prediction as to the energy that was
  required to produce them.  When the preponderance
  of individual bloodstain diameters are less than
  1mm, they are consistent with having been
  produced as a result of a high velocity impact. 
  Most often they would result from a shooting.
•   http//www.brazoria-county.com/sheriff/id/idtop
  .htm

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• When the preponderance of dozens of individual
  bloodstains are approximately 1mm or more in
  diameter, they are consistent with having been
  produced as a result of a medium velocity
  impact.  Most often they would result from a
  beating or stabbing.
•   http//www.brazoria-county.com/sheriff/id/idtop
  .htm

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• The shape of a bloodstain is a function of the
  angle at which it impacts a surface.  Perfectly
  round bloodstains result from a ninety degree
  impact.  The angle of impact of an elliptical
  bloodstain may calculated from its length  to
  width ratio.
•   http//www.brazoria-county.com/sheriff/id/idtop
  .htm

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• Bloodstains may often be lifted from the surface
  upon which they  have been deposited.  The harder
  and smoother the surface the more likely they may
  be successfully lifted.
•   http//www.brazoria-county.com/sheriff/id/idtop
  .htm

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• When measurements and angles are used to
  establish the origin or origins in space, not
  only will the actual origin be somewhere below
  the point or points of convergence, but it must
  be remembered that the investigator is
  determining a spatial volume and not a small pint
  of origin.
•   http//www.brazoria-county.com/sheriff/id/idtop
  .htm

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• Sobriety of the victim will have no significant
  effect on how bloodstain patterns are produced. 
  A high blood alcohol level is of no concern to
  the interpretation of bloodstain patterns.
•   http//www.brazoria-county.com/sheriff/id/idtop
  .htm

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• When blood is projected upward with sufficient
  force to strike a ceiling, it will almost always
  be the result of a gunshot having an upward
  trajectory.  Such a trajectory is more often the
  result of a suicide rather than it is a homicide.
• An exception is when dealing with cast-off blood
  patterns.
•   http//www.brazoria-county.com/sheriff/id/idtop
  .htm