JS 12B: Bloodstain Pattern Analysis

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JS 12B Bloodstain Pattern Analysis

• Announcements, Acknowledgements, Assignments
• Bloodstain Pattern Analysis
• Definition- pattern, size, shape and location
• Uses of bloodstain pattern analysis
• Properties of blood
• Categories of bloodstains- Passive, transferred,
  projected
• Target surface
• Angle of impact
• Point of convergence to determine origin
• CSI Bloodstain Pattern Exercises
• Stain as a function of volume, origin, target
  surface, impact angle, distance

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Announcements/Assignments/Acknowledgements

• Assignments Read Chapters Houde 8 and 9- Study
  for quiz
• Acknowledgements and References for more
  information
• Akin, L.2005.Blood. Interpretation at Crime
  Scenes. The Forensic Examiner. 146-10.
• Bevel, T and Gardner, RM. 2002. Bloodstain
  Pattern Analysis. 2nd ed. CRC Press.
• HemoSpat- Bloodstain Pattern Analysis Software
  http//hemospat.com/
• International Association of Bloodstain Pattern
  Analysis http//www.iabpa.org/
• IABPA (International Association of Bloodstain
  Pattern Analysts). Suggested IABPA Terminology
  List. Retr. 10/05 from http//www.iabpa.org/RevEd
  uc.pdf
• James, SH, Kish, PE and Sutton, TP. 2005.
  Principles of Bloodstain Pattern Analysis Theory
  and Practice.CRC Press.
• Slemko, J. BLOODSTAIN PATTERN ANALYSIS TUTORIAL
  Retrieved Spring 2005 from http//www.bloodspat
  ter.com/BPATutorial.htm
• Wolson, T. 2001. Bloodstain Pattern Analysis
  Workshop. Toby Wolson. Miami-Dade Police
  Department Course
• Wilkipedia The Free Encyclopedia. Bloodstain
  pattern analysis. http//en.wikipedia.org/wiki/Blo
  od_pattern_analysis_at_crime_scenes
• Optional Assignments for Extra Credit- Slemko
  2005 or Computers vs String - http//www.crime-sce
  ne-investigator.net/computersvstrings.html.
  Write a 500 word summary and 3Q and 3 A by Monday
  21 November for 1 extra credit point.

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The success or failure of any criminal
investigation often depends on the recognition of
physical evidence left at a crime scene and the
proper analysis of that evidence.
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Crime scenes that involve bloodshed often contain
a wealth of information in the form of
bloodstains. The pattern, size, shape, and the
location of such stains may be very useful in the
reconstruction of the events that occurred.
http//www.bloodspatter.com/BPATutorial.htm
William G. ECKERT and Stuart H. JAMES
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Bloodstain Pattern Analysis

• is the examination of the shapes, locations, and
  distribution patterns of bloodstains, in order to
  provide an interpretation of the physical events
  which gave rise to their origin.
• Based on the premise that all bloodstains and
  bloodstain patterns are characteristic of the
  forces that have created them

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Uses of Bloodstain Pattern Analysis

• Location and description of individual stains and
  patterns.
• Mechanism that created the stains
• Direction a blood droplet was traveling by
  calculating angles of impact
• Area of origin- location of blow into blood
  source
• Type of object used in the attack (blunt, edged,
  firearm, etc.)
• Minimum number of blows (First one is for free)
• Presence of a subject at a scene
• Positioning of the victim, suspect, and objects
  during events
• Sequence of events
• Confirm or refute assumptions concerning events
  and their sequencePosition of victim.
  (standing, sitting, lying)Evidence of a
  struggle. (blood smears, blood trails)
• Confirm or refute statements made by principals
  in the caseAre stain patterns on a suspects
  clothing consistent with his reported actions?
  Are stain patterns on a victim or at a scene
  consistent with accounts given by witnesses or
  the suspect?

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Properties of Blood

• On average, accounts for 8 of total body
  weight
• 5 to 6 liters of blood for males
• 4 to 5 liters of blood for femalesA 40 percent
  blood volume loss, internally or/and externally,
  is required for death
• A blood loss of 1.5 liters, internally or
  externally, is required to cause incapacitation.

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Properties of Blood 2

• Surface TensionThe elastic like property of the
  surface of the liquid that makes it tend to
  contract,caused by the forces of attraction
  between the molecules of the liquid.The cohesive
  forces tend to resist penetration and separation.

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Categories of Bloodstains
PROJECTED                                       
               
PASSIVE                                    
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Passive Bloodstains

• Passive Bloodstains are drops created or formed
  by the force of gravity acting alone. This
  category can be further subdivided to include
• Drops Drip patterns Pools Clots

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TARGET SURFACE TEXTURE Bloodstains can occur on
a variety of surfaces, such as carpet, wood,
tile, wallpaper, clothing, and the list goes on
The type of surface the blood strikes affects
the amount of resulting spatter, including the
size and appearance of the blood drops. Blood
droplets that strike a hard smooth surface, like
a piece of glass, will have little or no
distortion around the edge.
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Blood droplets that strike linoleum flooring take
on a slightly different appearance. Notice the
distortion (scalloping) around the edge of the
blood droplets.Surfaces such as wood or concrete
are distorted to a larger extent. Notice the
spinesand secondary spatter present.
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LARGE VOLUMES OF BLOOD (patterns created by same
volume of blood,from same source to target
distance)
"Projected Blood (through syringe)
                                                  
     
"Spilled Blood"                                 
             
"Dripped Blood"                                 
                
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PROJECTED BLOODSTAINS
Projected bloodstains are created when an exposed
blood source is subjected to an action or force,
greater than the force of gravity. (Internally
or Externally produced) The size, shape, and
number of resulting stains will depend,
primarily, on the amount of force utilized to
strike the blood source.
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Projected Bloodstains- This category can be
further subdivided to include
Arterial Spurt / Gush Bloodstain pattern(s)
resulting from blood exiting the body under
pressure from a breached artery
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.
Cast-off Stains Blood released or thrown from a
blood-bearing object in motion
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Projected Bloodstains Impact
Low Velocity Gravitational pull up to 5 feet/sec.
Relatively large stains 4mm in size and greater
Medium Velocity Force of 5 to 25 feet/sec.
Preponderant stain size 1 to 4mm in size
High Velocity Force of 100 feet/sec. and
greaterPreponderant stain size 1mm in size and
smaller Mist like appearance
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DIRECTIONALITY OF BLOODSTAINSWhen a droplet of
blood strikes a surface perpendicular (90
degrees) the resulting bloodstain will be
circular.That being the length and width of the
stain will be equal. 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.
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IMPACT ANGLE DETERMINATION ANGLE of IMPACT is
the acute angle formed between the direction of
the blood dropand the plane of the surface it
strikes
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2001 Miami-Dade PD Bloodstain Pattern Analysis
Workshop T. Wolson
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Bloodstain - Angle of Impact
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Determining the Angle of impact
Angle arcsin (Width/Length
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POINT OF CONVERGENCE AND ORIGIN DETERMINATION

• The common point, on a 2 dimensional surface,
  over which the directionalityof several
  bloodstains can be retraced.
• Once the directionality of a group of stains has
  been determined, it's possible to determine a two
  dimensional point or area for the group of
  stains.

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Point of Convergence
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Determining the Origin
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THREE DIMENSIONAL POINT OF ORIGIN DETERMINATION
WITH IMPACT ANGLE CALCULATIONS
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Training and Certification

• International Association of Bloodstain Pattern
  Analysts- Provides - 40 hour course to learn
  basics
• Additional training is required for
  certification from International Association of
  Identification
• Additional Training- Conferences, Seminars,
  Advanced courses
• Crime Scenes and Practical Experience

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Crime Scene Exercise Bloodstain Patterns

• Conduct each experiment in triplicate (3 drops)-
  Collect data indicated in the handout
• Bloodstain as a function of volume
• From 3 ft- small vs large volume
• Bloodstain as a function of origin
• From 3 ft- tip vs handle
• Bloodstain as a function of target surface
• Smooth vs Tile
• Bloodstain as a function of impact angle
• 3 angles
• Bloodstain as a function of distance
• 1 ft, 6 ft, Ceiling

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Uncertainty in the Estimated Angles of Impact of
Freely Falling Blood Drops

• Jon A. McGuire, MFS, and Walter F. Rowe, PhD
• Department of Forensic Sciences
• The George Washington University
• Washington, DC
• Presented at the Feb. 2005 AAFS Meeting held in
  New Orleans, LA

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The Balthazard Formula

• Crime scene reconstructionists and bloodstain
  pattern analysts frequently use the Balthazard
  formula for calculating the angle of impact of a
  freely falling blood drop with a target surface
  from the dimensions of the resulting blood spot
• Blood drops impacting a flat surface at an angle
  ? produce an elongated blood spot having length L
  and width W
• The angle ? is then given by the equation

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Determination of the Angle of Impact
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Uncertainties in Calculated Angle of Impact

• Books on bloodstain pattern analysis rarely
  discuss the uncertainties in the calculated angle
  of impact
• Bevel and Gardner suggest that the calculated
  angles are accurate to within five to seven
  degrees
• Bevel, T., Gardner, R.M., Bloodstain Pattern
  Analysis, 2nd Edition, Boca Raton, FL, CRC Press,
  2002.

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Goal of Research

• This research was undertaken to determine the 95
  and 99 confidence ranges for the estimated
  angles of impact of blood drops

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Materials and Methods

• Fifteen microliter drops of human blood were
  allowed to fall ten and thirty-six inches onto
  the uncoated surface of white poster board with
  impact angles of approximately 10, 20, 30, 40,
  50, 60, 70, 80 and 90 degrees
• Fifteen drops of blood were dropped at each angle
  of impact and each distance of fall
• Fifteen microliters was found to be the smallest
  volume of blood that would fall freely from the
  disposable tip of a Pipetman pipetter

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Materials and Methods

• Two different distances of fall were used to
  determine if the estimated angles of impact
  showed any dependence on the distance of fall
• Theoretically there should be no such dependence
• However, a height dependence up to 48 inches has
  been noted
• The untreated surface of the white poster board
  was chosen as the target surface to reduce the
  flow of the blood drops after their impacts

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Materials and Methods

• The target surface was held in a homemade device
  fabricated from Plexiglas and wooden dowel rods
• Slots were cut in the Plexiglas at various angles
  from 10 degrees to 90 degrees
• The angles of the slots were measured after they
  were cut

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Materials and Methods

• The lengths and widths of the blood spots were
  measured with a Cen-Tech 4 inch digital caliper
• Three (3) of the blood spots produced at an angle
  of impact of 80 degrees and a thirty-six inch
  distance of fall were discarded because their
  widths were greater than their lengths

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Materials and Methods

• The measured lengths and widths of the blood
  spots were used to calculate the angle of impact
  using the Balthazard formula
• The means and standard deviations of the
  calculated angles of impact were determined for
  each angle of impact and each distance of fall

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99 Confidence Range
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Conclusions

• The use of the Balthazard formula for the
  calculation of angles of impact has been
  statistically validated
• Up to an angle of impact of 60 degrees the
  uncertainty in the calculated angle of impact is
  less than 3 degrees
• This is substantially better than the uncertainty
  claimed by Bevel and Gardner
• The angles of impact calculated from the
  Balthazard formula are affected by the distance
  of fall

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Further Research

• The same validation procedure should be applied
  to other surfaces
• The effect of distance of fall on the calculation
  of the angle of impact should be explored further