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Bloodstain Pattern Analysis
Introduction to The Basics
Understanding the basics does not make one an expert!
Purpose of this lesson is to introduce you the topic of Bloodstain Pattern Analysis
The take home lesson
 ALWAYS archive bloodstain patterns because all bloodstain patterns contain
important investigative information
 Archiving
 Sketching is not satisfactory for documenting bloodstain patterns except to
show where they are and to record their breadth and width.
 These are patterns
 Archive photographically & using video
Multitasking Evidence
Provides investigators with a wide range of
possible investigative information.
Whose blood is at the scene
Distance from a target
Direction of travel
Energy of impact
Relative position and movement of victim and assailant
Minimum number blows
Sequence of events
and more
Historical Perspectives
BPA in the United States
 Blood leaves the human body or bloody covered object & produces interpretable
 Multiple scene types – Should expect to find at scenes of violent crimes and
 Interpreting what patterns reveal with respect to the events of the crime depends on
reliability of experts … the training and experience.
WHO Analyzes Bloodstain Patterns
 BPA has attracted individuals having diverse educational and professional
backgrounds. Why? This seems shocking for a discipline supposedly having a basis in
science. After all, shouldn’t science be practiced by scientists?
 The 2009 NAS report questions the scientific basis of pattern evidence, including
BPA, because conclusions are seemingly based more on experience than scientific
principle, even if the underlying basis of the conclusions is science-based.
Who Practices BPA?
 Much of forensics is an amalgamation or
partnership of forensic scientists and law
enforcement professionals
 Crime scene investigation is largest subdiscipline of forensics where science is practiced
mostly by non-scientists and some scientists, each
performing the same function.
Lay investigators
 Perform science at the scene,
 Adopted BPA as investigative
Crime laboratory scientists
 Participate in the scene investigative
scenario also adopted BPA as a subspecialty.
 Non-scene forensic biologists
Crime Scene
Criminalists … Others
Violent Crimes
BPA in the United States
 Began arguably at the University of
California Berkley with the work of Dr. Paul Kirk,
a well known and respected forensic scientist.
 Kirk investigated the 1950’s murder of Dr.
Sam Sheppard’s wife.
 Sheppard arrested and convicted of the
crime but always claimed that an intruder
entered his house and murdered his wife.
 Dr. Kirk went to the scene, wrote a
brief for the court and testified concerning
his belief that the bloodstain pattern
evidence showed someone else was at the
 Kirk’s work in the case has become a
legendary example of BPA.
More Historical Perspectives
 “Mockery of Justice”
 A book written by Sheppard’s son and Cynthia Cooper
produced spotty DNA evidence suggesting Kirk’s
interpretation was correct.
Kirk’s work went largely unnoticed by police officials and
crime scene investigators for whatever reason.
Perhaps law enforcement didn’t like his interpretations
 OR thought it incorrect
 OR considered his work esoteric and beyond the
skills of lay professionals, thus requiring a scientist of
Kirk’s caliber.
Workshops for Law Enforcement
 The next important work in this area was a booklet published by
Herbert MacDonell, “Flight Characteristics and Bloodstain Patterns of
Human Blood.”
 MacDonell’s experiments and research of other investigators
throughout the world - caught the attention of law enforcement.
 Taking advantage of that interest, MacDonell began offering
workshops designed to train law enforcement officers how to
interpret bloodstain patterns.
 The result has been a proliferation of individuals working BPA cases
throughout the United States.
 Most importantly, the simplicity of these workshops spawned a cadre
of self-styled experts who also offered workshops and published books
and articles.
Historical Overview – Cont.
 MacDonell’s workshops and others that followed presented BPA in
an easy-to-follow, lively and fun format, which was and continues to be
offered in a not so rigorous a format, at least from an intellectual
 No written examinations or other traditional grading
mechanisms, so no one feared failing the course.
 Everyone who attended and completed the course received a
certificate of attendance, many of whom began practicing BPA in
 By requiring not much more other than completing a week-long
course, attendees left with the feeling that BPA was simple enough
for them to practice.
 Recognizing the need for a formal organization around which the
growing hoard of BPA analysts could communicate,
 MacDonell was instrumental in establishing the International
Association of Bloodstain Pattern Analysts (IABPA). Now official
 Result of a proliferation of workshops
 On-going workshops and growing membership in the IABPA
resulted in a proliferation of lay investigators,
 Many with dubious scientific and/or investigative credentials
 Performing BPA in casework working on both sides of the
adversarial system.
 Ultimately their testimony has influenced the courts and thus has
played a critical role in determining innocence or guilt.
 The IAI split off BPA as a sub-discipline of crime scene investigation,
considering it a separate discipline and began offering certifications.
 National Research Council’s NAS report of 2009 questions the scientific basis
of BPA, practitioners dispute this.
Forensic scientists in Minnesota in forefront of bloodstain pattern research
and education reported in 2008 they believed BPA is a scientific endeavor. The
following was taken from the introduction in their article:
“The blood patterns that form from such events often have recognizable characteristics
that permit them to be classified into pattern types. It follows then that with a suitable
understanding of these characteristics, investigators can draw certain inferences about the
events and the mechanisms that led to the formation of the pattern.
“However, a bloodletting incident is often a complex set of events which take place in
three dimensional space. Blood volumes which are transferred generally undergo some change
prior to their subsequent deposition on a surface. For example, a pool of blood is broken up
into droplets of varying size which are projected outwards when the volume is subjected to an
impact force. It is our contention that an understanding of the dynamics of these changes is
critical to the sound interpretation of the resultant bloodstain pattern.
“To date, investigators have mainly relied on observing many such patterns, coupled
with laboratory simulation experiments, to build up experience in the recognition and
classification of bloodstain patterns. Relatively little however, has been documented about
the dynamics of the blood transfer event
 Labor and Epstein preempted the NAS report, warning other BPA analysts to
move quickly to strengthen the discipline.
“… it is reasonable to assume that the courts will continue to demand the highest
standards of forensic evidence and scrutinize with even more thoroughness each and
every method behind the opinion of an expert witness. BPA is a discipline that has
relied heavily on the experience of the witness. It is anticipated that a closer scrutiny
of the methods used in BPA will highlight the relative lack of underpinning scientific
research and validation studies.
“It is critical therefore, that the BPA community moves quickly to strengthen the
discipline with sound basic research to underpin the testimony of the analyst and give
the courts the confidence they need in this testimony …”
 Number of cases involving BPA increasing
 Standards needed:
 In 2002, the FBI began sponsoring a professional group devoted to
BPA, the Scientific Working Group on Bloodstain Pattern Analysis
(SWGSTAIN), whose mission is:
“… to serve as a professional forum in which BPA practitioners and practitioners from
related fields can discuss and evaluate methods, techniques, protocols, quality assurance,
education, and research relating to BPA.
 SWGSTAIN began formulating guidelines for practicing BPA.
 Logical place to begin was to standardize the terminology to create
standard way of communicating
 AND to minimize confusion surrounding terminology that had been
adopted ad hoc over time.
 Interestingly, the SWGSTAIN final version was not published until 2009,
after publication of the NAS report
Scientific Basis of BPA
Scientific Basis of Bloodstain
Pattern Analysis
 If BPA has basis in science, testimony should be admitted into evidence
 Testifying expert analyst must meet appropriate standards
 Must have as yet undefined credentials.
 Understanding basis of BPA
 Gained through education and experimentation while employing the principles
of the relevant scientific disciplines: biochemistry, fluid mechanics (dynamics),
physics, chemistry, ballistics, and mathematics.
 These disciplines form the scientific basis of BPA, and their principles
must be able to explain why blood forms the patterns it does.
 If cannot, then BPA does not have a basis in science and must be considered
 The scientific basis must yet be proven: SWGSTAIN provides references
designed to document the scientific basis of BPA.
 To address the topic properly, first understand the nature
of blood, which requires knowledge of biochemistry.
Classification of Blood
 Viscoelastic, Newtonian fluid.
 Understanding what happens to it after it leaves the human
 Whether acted upon by a force or just passively dripping
from an object,
o Requires more than casually observing bloodstain
formation empirically in a workshop setting or in the field.
 In depth knowledge of the biochemistry of blood
Blood Composition and Surface Tension
 Composition:
 Blood plasma composed of macromolecules (proteins, carbohydrates, water
and other dissolved salts and other molecules).
 Its physical properties – viscosity and surface tension – are mainly
determined by dissolved macromolecules in the blood’s plasma.
 Surface tension is the force that makes blood droplets (or any liquid)
maintain its integral structure,
 Blood retains its shape until acted on by a force that overcomes the surface
 The force that overcomes surface tension creates blood spatter and thus the
patterns observed at crime scenes.
 How the force is applied and its strength determines the visual
appearance of the resulting pattern.
To See
Demonstration of
Surface Tension,
 The laws of physics apply to blood droplets in flight
 Direct application to blood droplet formation and its flight
characteristics should be well understood.
 These considerations have been taken for granted
 Mostly from empirical studies in a workshop setting.
 Few publications document whether blood flight conforms
to the laws of fluid dynamics.
Fluid Dynamics
 Fluid mechanics (dynamics). Study of fluids (liquids, gases and
plasmas) and the forces acting on them.
 Its laws define blood in motion after being acted on by a force.
 Bloodstain spatter forms from liquid blood in motion
o Fluid dynamic computations describe blood in motion
 The bottom line is that every drop of blood at the crime scene can
and perhaps should be described mathematically.
 Although publications exist, such a study has not been done
Terminal Velocity.
A concept of fluid dynamics.
 A blood droplet reaches
terminal velocity (settling velocity)
when speed becomes constant,
Downward force of gravity
equals upward force of drag.
Single drops of blood falling from fingertip
onto smooth cardboard from various heights.
 When a blood droplet’s
Little change in diameter beyond 7-8 ft.
speed is constant, drag equals
the droplet’s weigh, and its
acceleration is zero.
When a blood droplet reaches its terminal
velocity, the stain on a hard, smooth surface, will
 For bloodstains falling from
have a constant diameter, regardless of the
identical heights and having a
height from which it falls.
constant weight (volume), their
terminal velocities will be identical. Generally, terminal velocity occurs at
approximately 20 feet.
 Experiments show that bloodstain
diameters change very little after falling
approximately 8 feet.
Trajectory Analysis (ballistics)
 Blood leaving human body under a force forms an arc
 Path described mathematically.
 Blood droplet represents a projectile
 Path is its trajectory.
 Like a bullet, the arc a blood droplet takes to its final terminus is
dependent on gravity, wind currents, temperature, humidity and friction.
 In real world, other considerations exist:
 non-uniform gravitational forces,
 air resistance (friction) – drag and aerodynamics, create an
arc pattern that is not parabola.
Gravitation (Gravity)
One of four fundamental interactions of nature
 Strong and weak interactions, electromagnetism and gravitation
o Where objects having mass attract one another. The force that
causes objects to fall to the ground when dropped.
o Keeps planets in their obits around the sun and the moon around the
Described by the general theory of relativity that governs the motion of inertial
Causes dispersed matter to coalesce,
 When the earth and other planets formed after the Big Bang.
Defines the path blood droplets take (non-gravitational influences not
considered) until they interact with an object and comes to rest.
From a bloodstain perspective,
Gravity is responsible for the natural convection by which fluid flow occurs.
Influence is most apparent in the visual pattern of blood present at scenes as
well as the pooling and flow of blood.
Centripetal Force
Only Force Work.
 Directed toward the center of the path
of the moving object.
 Adhesive forces hold blood onto
 Blood flies off object tangentially
o When adhesive forces are
greater than the centripetal force,
 This is a straight line
 The impact site and its angle
are a direct link to the location of
the object at the exact moment
the blood left.
Fundamental Principles
of Bloodstain Analysis
Surface Tension and Droplet Shape
Accumulates until
Surface tension pulls
vertically &horizontally
to keep droplet together
Settles into a Sphere
Angle of Impact
Determining the Direction of Blood
Travel and Angle of Impact of
Individual Droplets
 Falling downward (90o)
 Forms circle,
 Depending on the texture of the surface
(smooth, textured, dusty, etc), its edge
characteristics has varying amounts and
intensity of scalloping.
 As impact angle becomes more and more
acute, stain elongates and can form a tail points
in the direction droplet was traveling.
 In this way, it is a simple matter to determine
the direction from which blood droplets in the air
were moving
Adapted from
Introduction to Forensic Sciences,
W. Eckert, CRC, 1997
Dynamics of Droplet formation
Effect of Oblique Impact
 Pizzola and Deforest defined what
happens to blood when it strikes an angled
surface …
 Demonstrated mechanism of how
blood interacts with a surface to form
the specific patterns encountered at
crime scenes
Blood or Drip Trails
 According to SWGSTAIN terminology, a drip
trail is,
“A bloodstain pattern resulting from the
movement of a source of drip stains between two
 When blood drips from object in motion, the
resulting droplet shapes can range from nearly
circular (falling nearly perpendicular to the
surface) to elongated (hitting the surface at an
angle) depending on the speed of the travel.
 If droplets form elongated stains, direction of
travel direction the stain points. The tail points
toward movement of droplet.
 However, for objects moving slowly the
droplets can be nearly circular, mimicking droplets
falling from a height.
Drip Trails - Continued
 Examine edge characteristics of the resulting stain,
 Direction depends on texture of the interacting surface – smoothness.
 Edge characteristics show direction of travel to a greater or lesser
 Texture of the interacting surface, determines degree of scalloping,
presence of spines and/or associated satellite stains.
o Extremely smooth surfaces:
 Edge characteristics of droplet minimal or almost
o Textured surfaces:
 Droplets have edge characteristics that are not smooth:
they will have scalloping and may have spines or even satellite
stains associated with them.
 Direction of travel
 Leading edge of stain has preponderance of spines and/or satellite
 Pointing in the direction of the movement.
 Relying on a single droplet in a drip trail to determine the direction of movement can lead to
either misinterpretation. Visible scalloping on the left, suggesting it originated from someone moving
right-to-left. However, edge scalloping is present on the right side of the droplet stain - in the lighter
Confusing because concentration of blood on the left side of droplet suggests a left slant
to the floor.
Actually floor is horizontal
Lighter colored area occurred because droplet repelled by wax on freshly waxed floor.
 Closer inspection of the light area
shows scalloping and small satellite stains,
the latter suggesting movement from leftto-right.
 Correct interpretation
 Interpreting direction as moving
right-to-left … incorrect.
 If other stains in the trail were
equally as confusing as stain in
photograph, the logical interpretation
would be inconclusive.
Shape & Size of Bloodstain Droplets
 Shape - Target surface
 texture (rough or smooth)
 Affects shape of droplet
 Collisions with surfaces that are not
 The roughness of the surface
overcomes the surface tension
holding the droplet together.
T- shirt
 Size
 Volume of the droplet
 Distance fallen
o Little change in diameter beyond 8 feet
 Absorption/porosity
 More absorptive, better spreading of
droplet into surface
 Thickness
 Thick , absorptive surface pulls
droplet into matrix & keeps from
Surface Characteristics & Droplet Shape
Single Droplets Falling onto Various Surfaces
Sattelite Stains
400 Grit
Droplet on Wood
150 Grit
Droplet on Velcro
Perimeter Stain: Ghosting or Skeletonization
 Droplet begins to dry when landing of any surface. Over time it will dry.
 Drying begins from the outside edge toward the middle.
 Outside edges are shallower and lose water faster than middle of droplet
 Brushing something across drying droplet, edges form an outline.