Transcript Chapter10 blood stains v2

Chapter 10
CRIME SCENE
RECONSTRUCTION:
FORENSIC BLOODSTAIN
PATTERN ANALYSIS
Crime Scene Reconstruction
• The method used to support a likely sequence of
events by the observation and evaluation of
physical evidence, as well as statements made by
those involved with the incident, is referred to as
reconstruction.
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By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
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Initial Walk Through
• What should you try to answer on the initial
walk through of a crime scene?
– What occurred?
– Where did it happen?
– When did it happen?
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
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Initial Body Exam
• . When a medical examiner first examines a
corpse at a crime scene it is important to
note the livor mortis. What could it
indicate if it is anywhere other than the
lowest part of the body? That the body
had been moved after death.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
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What Happened?
• Crime-scene reconstruction relies on the
combined efforts of medical examiners,
criminalists, and law enforcement personnel
to recover physical evidence and to sort out
the events surrounding the occurrence of a
crime.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
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Forensics Team Members
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
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Stain Patterns of Blood
• The crime scene investigator must remember that
the location, distribution, and appearance of
bloodstains and spatters may be useful for
interpreting and reconstructing the events that
produced the bleeding.
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By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
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Document the Crime Scene
• You will need to document the crime scene
to allow for later reconstruction to let the
evidence tell the story of what happened.
• You document the scene with:
– Photos/ video
– Drawings
– Notes of observations
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
10-8
Bullet Path with a Laser
• A criminalist can use a laser in the initial
analysis to determine the bullet path.
•
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
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Blood Stains Tell a Story
• What 6 pieces of information could one
deduce from the bloodstain pattern at a
crime scene?
–
–
–
–
–
–
direction of blood origin,
angle the blood struck a surface,
location of a victim,
movement of a bleeding individual,
minimum number of blows on the victim
approximate location of the one delivering the
blows
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
10-10
Mathematical Equation for
Blood Stain Angles
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
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Blood Fall Height
• . What does the initial height of the blood
drop do to the pattern of blood drops? the
higher the drop, the bigger the velocity and
the larger the diameter.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
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Low Velocity Spatter
• The characteristics of a low velocity spatter
are the pattern consists of large separate or
compounded drops with diameters of 3 mm
or more. produced by minimal force and
hits the surface with less than 5 ft/s velocity
Dripping Blood from a wound.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
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Medium Velocity Blood Splatters
• The characteristics of a medium velocity
spatter consists of small drops with
diameters of 1 -3 mm. they travel at an
average of 5 to 25 ft/s
• They are commonly associated with blunt
force trauma.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
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High Velocity Blood Splatters
• The characteristics of a high velocity spatter
are that it consists of drops with diameters
of less than 1 mm. This blood spatter hits at
more than 100 ft /s. Gunshot spray.
• Video
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By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
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Arterial Spray Pattern
• Arterial spray is caused
by opening a major
artery or the heart and it
sprays out a large
volume of blood with
each heart beat. It has
enough force to have a
major spurted volume
with flow patterns
surrounded by radial
spikes and satellite
droplets.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
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Blood Stains
• Surface texture and the stain’s shape, size,
and location must be considered when
determining the direction, dropping
distance, and angle of impact of a
bloodstain. Reference Link
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
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Stain Patterns of Blood
• Surface texture is of paramount
importance. In general, the harder and less
porous the surface, the less spatter results.
• The direction of travel of blood striking an
object may be discerned because the
pointed end of a bloodstain always faces
its direction of travel.
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©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
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Angled Impacts
• The impact angle of blood on a flat surface
can be determined by measuring the
degree of circular distortion. At right
angles the blood drop is circular, as the
angle decreases, the stain becomes
elongated.
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By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
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Stain Patterns of Blood
• The origin of a blood spatter in a twodimensional configuration can be established by
drawing straight lines through the long axis of
several individual bloodstains. The intersection
or point of convergence of the lines represents
the origin point.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
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Stain Patterns of Blood
• A shooting may leave a distinct gunshot spatter
pattern. This may be characterized by both
forward spatter from an exit wound and back
spatter from an entrance wound.
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By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
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Back Spatter from Gun Shot
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By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
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Wound Characteristics
• The location of injury, the size of the wound
created, and the distance between the victim and
the muzzle of the weapon all affect the amount of
back spatter that occurs.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
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Cast Off Patterns
• A cast-off pattern is created when a blood-covered
object flings blood in an arc onto a nearby surface.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
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Arterial Spray Pattern
• Arterial spray spatter is created when a victim
suffers an injury to a main artery or the heart.
Commonly, the pattern shows large spurted stains
for each time the heart pumps.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
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Expirated Patterns of Blood
• A pattern created by blood that is expelled from the mouth
or nose from an internal injury is called an expirated blood
pattern.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
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A Void Pattern
• A void is created when an object blocks the deposition of
blood spatter onto a target surface or object.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
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Transfer and Contact Patterns
• When an object with blood on it touches one that does not
have blood on it, this produces a contact or transfer pattern.
• Examples of transfers with features include fingerprints,
handprints, footprints, footwear prints, tool prints, and
fabric prints in blood.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
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Stain Patterns of Blood
• Patterns made by drops or large amounts of blood flowing
by the pull of gravity are called flows.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
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Skeletonization Blood Pattern
• A pool of blood occurs when blood collects in a level (not
sloped) and undisturbed place.
• The edges of a stain will dry to the surface, producing a
phenomenon called skeletonization.
• .
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
10-30
Trail Pattern of Bloodstains
• A trail pattern is a series of drops that are separate from
other patterns, formed by blood dripping off an object or
injury
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
10-31
Documenting Bloodstain Evidence
• Investigators should note, study, and photograph each
pattern and drop of blood to accurately record the location
of specific patterns and to distinguish the stains from
which laboratory samples were taken.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
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Documentation
The investigator should create photographs and sketches of
the overall pattern to show the orientation of the pattern to
the scene.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
10-33
Grid Method
• Two common methods of documenting bloodstain patterns
are the grid method and the perimeter ruler method.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
10-34