Bloodstain Pattern Analysis
©2007 Vernon J. Geberth, Practical
Homicide Investigation
Reprint: Law and Order, Vol. 55, No. 3, March,
2007
Article Expanded for Research
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Materials
INTRODUCTION
Bloodstain pattern analysis can
range from the simple to the complex. The trails of blood in a crime scene or
castoff blood patterns are reasonably straightforward and understandable.
Determining areas of convergence and origin employing string methods or
trigonometric methodologies are more complex and call for a trained specialist.
The scientific analysis of bloodstain patterns requires extensive training and
experience, which goes beyond the normal crime scene process. Furthermore,
there are a number of different definitions and opinions by various experts in
the field, which tend to confuse the average investigator. Therefore, the
author's intention within this article is to illustrate some simple and
practical examples of bloodstain pattern recognition and documentation along
with photos and description.
The terms used to describe bloodstain
patterns, are oftentimes confusing to the average investigator. Such terms as
bloodstain spatter or splatter might be used interchangeably. The
reference to pattern analysis or pattern interpretation further
confuses the issue because the word interpretation connotes subjectivity to the
scientific analysis and evaluation of bloodstain pattern evidence. According to
the recognized experts in the field the proper term is Bloodstain Pattern
Analysis (BPA), which implies a structured approach in evaluating that,
which is to be examined. It is one of several specialties in the field of
forensic science. The science of bloodstain pattern analysis applies scientific
knowledge from other fields to solve practical problems. Bloodstain pattern
analysis draws on biology, chemistry, math, and physics among scientific
disciplines
UNIVERSAL PRECAUTIONS
Investigators and crime
scene technicians need to be cognizant of the potential dangers in handling
blood and other biological fluids in the crime scene. The presence of airborne
pathogens and other biohazards such as AIDS, hepatitis and hepatitis B,
meningitis and even tuberculosis create a potential risk. Investigators should
adhere to the following procedures at any crime scene where blood or body
fluids are encountered.
The CSI should wear approved disposable gloves
while in the crime scene and remain aware that blood and other body fluids may
carry diseases. Consider wearing a disposable mask while in crime scenes where
airborne communicable diseases such as meningitis or tuberculosis might exist.
Wear eye protective and disposable infectious disease gown to protect clothing
when exposed to large amounts of blood or other body fluids.
After the
investigation is complete, dispose of gloves, masks, and gowns contaminated by
blood or body fluids in a biohazard bag and wash hands thoroughly
with an antiseptic hand rinse. Before returning to the station, wash hands
again with water and a bacterial liquid hand wash, i.e., Bacti-Stat. Restrict
the number of investigators on the scene who may come in contact with the scene
of the potential infection exposure. Advise any investigators on the scene who
may come in contact with the scene of the potential infection exposure.
Decontaminate all equipment used prior to your return to the station.
Change clothing contaminated with blood or other body fluids immediately and
decontaminate. Dispose of contaminated supplies as recommended in this
protocol. Skin provides a very effective barrier for the prevention of
infectious diseases. Wash all contact areas as soon as possible after exposure
to help prevent contamination. Wounds such as cuts, sores, and breaks in the
skin, regardless of the size, provide an entrance for infection into the body
and should be properly bandaged. Report all significant exposures to blood or
other body fluids within 24 hours of exposure.
BLOODSTAIN
PATTERN EVIDENCE AT THE SCENE
Blood is present in most crimes scene
involving violence and therefore presents the investigator with additional
information to determine the sequence of events, which may have taken place
between the victim and the assailant. Bloodstain patterns at the scene or from
the clothing of principals in a case can be used to confirm or refute
assumptions concerning events and their sequence. In addition, bloodstain
patterns can illustrate the position of the victim, such as standing, sitting,
or lying. Bloodstain evidence can also show evidence of a struggle.
Furthermore an effective bloodstain pattern analysis can confirm or refute
statements made by principals in the case. For example, "Are stain patterns
on a suspects clothing consistent with his reported actions? Or, "Are
stain patterns on a victim or at a scene consistent with accounts given by
witnesses or the suspect"?
Locard's
Principle
Locard's Principle that the perpetrator will take away
traces of the victim and the scene, the victim will retain traces of the
perpetrator and may leave traces of himself on the perpetrator and the
perpetrator will leave behind traces of himself at the scene many times is
borne out in the evaluation and retrieval of bloodstain pattern
evidence.
The prosecution presented an excellent example of Locard's
Principle during the O.J. Simpson case. The "Trail of Blood" theory based on
the DNA analysis indicated that blood drops at the scene of the double murder
of Nicole Brown Simpson and Ron Goldman, as well as blood in O.J. Simpson's
Ford Bronco and his residence positively identified O.J. Simpson as the
suspect. The DNA analysis of three stains on the console of Simpson's Ford
Bronco indicated that droplets were a mixture of blood from Mr. Simpson, the
blood of his ex-wife Nicole Brown, and the blood of Mr. Ron Goldman. The famous
"bloody gloves" that were presented as evidence provided the crucial linkage.
One glove was found at Bundy Drive, the scene of the double homicide. The
matching right hand glove was found at O.J. Simpson's estate. DNA testing of
the glove found at O.J. Simpson's estate indicated that blood matching Simpson
and the two murder victims "linked" him to the murders. DNA testing of the
blood on the glove at Bundy Drive matched O.J. Simpson. The socks found in O.J.
Simpson's bedroom bore traces of blood from O.J. Simpson and his ex-wife
Nicole, who was one of the murder victims.
Crime scene reconstruction
and the presence of bloodstains and patterns in the scene are very important
considerations in the crime scene search process. The discipline of bloodstain
pattern analysis (BPA) considers the location, shape, size, distribution
and other physical characteristics of the bloodstains in the scene. Blood flows
will always obey gravity. Hence, the presence of blood flow that seemingly does
not follow ordinary gravitational pull might indicate movement of the victim or
disturbance of the scene by the offender or someone else who arrived in the
scene after the event including first responder.
In Practical
Homicide Investigation® we encourage first responders and detectives to
"Freeze" the scene so that everything is as it was when first discovered
in order to assure the recovery of any evidence. Crime scene technicians and/or
the ERT's focus on properly documenting the crime scene, through crime scene
photographs and crime scene sketches, the recovery and retrieval of crucial
evidence and the recognition and classifications of bloodstain evidence to
reconstruct events.
He or she is not expected to be able to perform the
sophisticated analysis that an expert in bloodstain pattern analysis performs
as part of their expertise and training. In some cases the person processing
the scene does in fact have the expertise to conduct bloodstain pattern
analysis. In either event, the most important concern is the documentation
through photographs and diagrams of any bloodstain pattern.
THE
PROCESSING OF THE CRIME SCENE
The search of the crime scene is the
most important phase of the investigation conducted at the scene. The retrieval
of bloodstain pattern evidence begins with the effective search of the
scene. Physical evidence refers to any tangible article, small or large,
which tends to prove or disprove a point in question. It may be used to
reconstruct the crime, identify participants, or confirm or discredit an alibi.
Homicide and sexual assault crime scenes usually contain an abundance of
physical or trace evidence especially bloodstain pattern evidence. The
systematic search, collection, and preservation of physical evidence are the
goals of the crime scene search.
TYPES OF PHYSICAL
EVIDENCE
Transient Evidence is temporary in nature. It can
include odors, temperature, imprints and indentations in soft or changing
materials such as butter, wet sand, snow or mud. It also refers to markings
such as lividity, or blood spatters on moveable objects. Pattern
Evidence is produced by contact. Blood splatter, glass fracture patterns,
fire burn patterns, Furniture position patterns, projectile trajectory, tire
marks, M.O., clothing or article patterns, and powder residue patterns are
considered pattern evidence. Conditional Evidence is caused by an action
or event, such as lighting conditions at a crime scene, odor, color, direction
of smoke; flame (color, direction, temperature); location of evidence including
bloodstain evidence in relation to the body. Transfer Evidence is
generally produced by the physical contact of persons, objects, or between
persons or objects. It is characterized by the LINKAGE CONCEPT.
BLOODSTAIN PATTERN ANALYSIS
CLASSIFICATION OF BLOODSTAIN SPATTER
BY VELOCITY
There are three basic categories of stain groups based
on the concept that the size of the bloodstain compared with the amount of
force propelling that bloodstain. These categories refer to the nature of the
impact or force causing the stain.
Low-Velocity Impact Blood Spatter
(LVIS)
Low-velocity is considered to be a force or energy
equivalent to normal gravitational pull up to a force or energy of 5 ft/s (five
feet per second). The resulting stain is relatively large, usually 4 mm in
diameter or greater.
Medium-Velocity Impact Spatter
(MVIS)
Medium-velocity is considered when a source of blood is subjected
to a force of from five to twenty-five feet per second. The resulting stains
range from 1 to 4 mm in diameter. These type stains are usually associated with
beatings or stabbings.
High-Velocity Impact Spatter
(HVIS)
High-velocity bloodstains are created when the source of
blood is subjected to a force with a velocity greater than 100 ft/s. (100 feet
per second). The resulting stain is predominantly less than 1 mm in diameter
although smaller and larger stains may be observed. These type stains are
usually associated with gunshot injuries.
|
| Multiple spatter pattersn in different forms. There is low-velocity drip, medium velocity drip near toilet bowl, and high velocity on the floor and pooling near the tub. |
CLASSIFICATION OF BLOODSTAINS THROUGH
TAXONOMY
Practically speaking, the low-medium-high velocity terms
can be confusing and have sometimes been used interchangeably. The future of
bloodstain pattern analysis will be based on description. Bloodstain pattern
analysis (BPA) has established classifications of stains known as
taxonomy of stains and the experts in the field have established the
classification of bloodstains and patterns based on a taxonomic approach.
A taxonomy is defined as a set of laws or principles for
classification. The idea of taxonomy is derived from biology where organisms
are classified by shared characteristics of varying degrees that also share a
hierarchical relationship. The hierarchical nature of the taxonomy is
significant in its application. At the top are broad categories. Moving down
the hierarchy, the criteria become more and more refined and thus the
conclusion about a classification becomes more distinct.
The
bloodstains and patterns are classified based on their physical features of
size, shape, location, concentration and distribution. Classification however,
is but one step in the overall analysis. Classification sets the stage for the
analyst to define more effectively a source event for any given stain.
DEFINTION OF TERMS
Gardner and Bevel (In Press and 2004)
have grouped bloodstain patterns into two basic categories; Passive
stains and Dynamic stains.
Passive
Stains
Passive stains result from an action other than a directed
force to a blood mass. Examples would the bloodstain found in a crime scene
from transfer or loss of blood by the victim. Blood dripping, contact with
bloody objects, which can further be categorized as contact patterns, drip
patterns, drip trails, blood pools or flows or blood clots.
Dynamic
Stains
Dynamic stains are created by forceful events where fluid
blood is projected out from a source under some force or compression. Dynamic
bloodstain patterns include spatter, castoff patterns, arterial patterns, and
splashes. There is an impact mechanism or projection of fluid. Examples of
dynamic stains would be Spatter Patterns, Castoff Patterns, Arterial Patterns,
Wipe and Splash Patterns, etc.
CLASSIC BLOODSTAIN PATTERNS
Spatter Patterns occur when a blood mass is broken up into
droplets. The droplets are projected out from the origin to the surrounding
surfaces within the scene. Blood spatter can occur on a variety of surfaces,
such as carpet, wood, tile, wallpaper, clothing, etc. The type of surface the
blood strikes affects the amount of the resulting spatter, including the size
and appearance of the blood drops. Also how the blood was deposited such as
dripping blood, spilled blood or blood, which has been projected.
Projected bloodstains are created when an exposed blood source is
subjected to an action or force, greater than the force of gravity. The size,
shape, and number of resulting stains will depend, primarily, on the amount of
force utilized to strike the blood source.
Directionality
When a droplet of blood strikes a surface
perpendicular (90 degrees) the resulting bloodstain will be circular thus the
length and width of the stain will be equal. However, when blood strikes a
surface at an angle less than 90 degrees the stain will be elongated or have a
teardrop shape. It is readily apparent to the trained eye of the homicide
detective. For instance the teardrop shaped stains with pointed end always
points in the direction of travel.
 |
| This graphic illustrates directionality. Passive Blood drop 90 degrees. Dynamic Blood drop with blue arrow indicating direction of travel. Courtesy of Nucleus Medical Art, Inc. |
Cast-off Bloodstains
Cast-off bloodstains
occur when blood is projected or thrown onto a surface from a bloody object in
motion. Examples would be a cast-off from a bloody hammer, baseball bat or
other blunt force instrument. Cast-off patterns are usually associated with
beating events. Cast-off bloodstains to a certain extent are consistent in size
within any given pattern but can vary depending on the size of the weapon, the
extent of the bloody injury and the force of the blow.
 |
| Cast-off blood stains on the ceiling and ceiling light fixture caused by blunt force instrument. |
Arterial Patterns
Arterial patterns result from
blood projected into the scene under pressure form the artery or heart. There
are distinctive physical characteristic in the arterial patterns, marked with
the typical bright red color of oxygenated blood, as well as the spiked
appearance of the blood being released under pressure from the breached artery.
These patterns are referred to as arterial spurt, spurting or arterial gushing
and are used interchangeably.
Pattern Transfer
Pattern
transfer occurs when the wet bloody object comes into contact with another
surface.
Splash Patterns
Splash patterns occur when a
volume of blood is projected into a scene with minimal force characterized by a
large central stain exhibiting minimal distortion. There will be very little
satellite spatter present. They most often appear as large-volume
patterns.
Wipe Patterns
A wipe pattern occurs when an
object moves through a preexisting bloodstain. Sometimes the object that wiped
through the blood can be identified, for example a broom. In addition the
direction can be ascertained.
Saturation
Patterns
Saturation patterns occur when blood had been drawn into
porous materials such as rugs, cloth, and clothing and usually tend to destroy
other blood patterns of interest.
Body Image
Body image
patterns occur when the bleeding body has been lying in the blood, which seeps
from the wounds. The blood pools form around the outline of the body and as the
blood solids separate from the serum the original position of the body is
imaged on the surface.
DOCUMENTING BLOODSTAIN PATTERNS
If
the crime scene technician is not trained in bloodstain pattern analysis it is
imperative that the crime investigators obtain complete documentation of any
bloodstains or patterns both with and without rule of measure. Never assume
that all the bloodstain patterns belong to the victim. This is particularly
true in cases involving multiple stabbings with sharp-edged instruments or
weapons. Self-wounding by the offender is a common occurrence. There are some
of the classic patterns such as Directionality, Cast-off Bloodstains, Swipe
marks, Pattern Transfer, Saturation, Arterial Patterns, Drip Patterns and other
examples of bloodstain dynamics, which should noted and documented by the
investigator at the scene.
Photographing the Bloodstain Evidence
Recording the bloodstain patterns in the scene is a major facet of
the investigation. It is extremely important that this be accomplished before
anything is touched or moved at the scene. Photographs should be taken
depicting the overall scene followed by medium range and close-up views of the
patterns. A scale of measure should be included with the close-up photographs.
Sketches and Diagrams
The crime scene sketch is a
simple line drawing that indicates the position of the body in relation to
fixed and significant objects in the scene. It supplements both
the written reports and the crime scene photographs. Photographs, because of
camera perspective and distortion, do not always depict the exact location in
which objects are situated or the relation of one object to another. The crime
scene sketch is an excellent visual aid, which allows for the removal of
unnecessary details and the inclusion of significant material. A sketch f the
bloodstain pattern will contain only essential items necessary for the
analysis, whereas regular crime scene photographs will be overcrowded with
detail.
Conclusion
Bloodstain Pattern Analysis (BPA) is a
discipline, which requires formal training coupled with years of practical
experience. The discipline of bloodstain pattern analysis considers the
location, shape, size, distribution and other physical characteristics of the
bloodstains in the scene. The Scientific Working Group on Bloodstain Pattern
Analysis entitled (SWGSTAIN) was created in 2002 and has established many of
the current protocols.
As the author of Practical Homicide
Investigation and Series Editor I encourage investigators to develop an
understanding of the applied science of BPA, which can produce strong,
solid evidence. I also recommend the following textbooks on BPA. They
are Bloodstain Pattern Analysis: With An Introduction to Crime Scene
Reconstruction. Second Edition by Tom Bevel and Ross Gardner (In Press 3rd
Edition), The Principles of Bloodstain Pattern Analysis: Theory and Practice
by Stuart James, Paul Kish and T. Paulette Sutton and Practical Crime
Scene Processing and Investigation by Ross Gardner.
Vernon J. Geberth, M.S., M.P.S. author of the New and
Completely Revised textbook, Practical Homicide Investigation: Tactics,
Procedures, and Forensic Techniques, FOURTH EDITION, 2006.
References
Bevel, T and Gardner R.,
Bloodstain Pattern Analysis with an Introduction to Crime Scene
Reconstruction, 2nd Ed, Boca Raton,
FL: CRC Press, LLC Inc., 2002
Gardner, Ross M. Practical Crime Scene
Processing and Investigation. Boca Raton, Florida:
CRC Press, LLC Inc., 2004.
James,
Stuart et. al. Principles of Bloodstain Pattern Analysis Theory and
Practice, Boca Raton,
FL: Taylor
& Francis CRC Press, 2005.
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