Serology PPT forensics

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Transcript Serology PPT forensics

Allie Wheeler, Amber Conrad, Aleisha Murrell,
Harsha Pinnamaraju, Orin Sparks, Jonathan Huynh,
Kyle Eberle
Table of Contents
 Introduction…1
 Objectives and Goals…2
 Educational Requirements…3
 Analytical Procedure…4
 Presumptive Test…5
 Blood Typing…8
 Interpreting Blood Stain Patterns…12
 Crime Scene Reconstruction…16
 Glossary…23
 The following information presented is to help understand
serology, the study of blood, in forensic science. Blood is the
most common piece of evidence found at a crime scene and
is key to solving any crime. The following information is
 Blood Typing
 Blood Spatter
 Crime Scene Reconstruction
 Educational Requirements to be an Expert in this Field
 And much more!
Objective and Goals
 Forensic Serology is dedicated to providing forensic analysis
of physical evidence to the criminal justice system.
 Specialists analyze evidence, usually associated with blood, to
identify any suspects.
 Tests and analysis are performed in controlled environment
using proper procedures in order to get accurate and relevant
analytical results.
Educational Requirements
 Requirements for a general careers in this field:
 formal education equivalent of a bachelor's degree in chemistry
or closely related field
 bachelor's degree in biology
 two years experience in a forensic laboratory
 approval of the S.O.M.
 School of Medicine
Analytical Procedures
 Collection from Clothing or Other Items
 Visual examine item
 Take care to preserve evidence and other sections
such as blood, stains, and latent prints
 At this point, you may use tape to remove stray
hairs and dust off the fiber
 Label tape lifts
 Identify fiber type and color
 Place in envelope to store
Presumptive Tests
 They are preliminary tests/field tests
 Establishes possibility of a specific bodily fluid’s presence
 Do not conclusively prove the presence
 Pros:
 Narrows possibilities
 Can be used on larger areas
 Can locate possible evidence not visible to naked eye
 Cons:
 Risk of false positives and may be overly sensitive
Presumptive Tests
 Phenolphthalein Test
 Aka: Kastle Meyer Test
 A Phenolphthalein solution is used to show
the possible presence of blood based upon a
reaction of hemoglobin which produces a
pink color.
 Precautions: This test is presumptive
because it has produced false positives
Presumptive Tests
 LuminolTest
 Luminol is used in solution or sprayed onto suspected surfaces.
This compound gives a strong blue fluorescence (glows)when
viewed with a UV light. It is used o find blood reminants
 Precautions: False positives have been observed with the
presence of copper salts
Blood Typing
Blood Type
Antigens of Red Blood
Antibodies in Serum
Anti- B
Anti- A
Neither Anti- A nor Anti- B
Neither A or B
Both Anti- A and Anti- B
Anti- A Serum
Anti- B Serum
Whole Blood
Whole Blood
Antigen Present
Blood Type
A and B
Neither A nor B
Universal Types
 People with type AB blood are called universal recipients
 No antibodies present
 Can receive blood from anybody
 People with type O blood are called universal donors
 No antigens present
 Can donate blood to anybody
Interpreting Blood Stain Patterns
 Satellite Spatter: Small droplets of blood that are
distributed around the perimeter of a drop/drops
of blood and were produced as a result of the
blood impacting the target surface
 Skeletonization: The outside of a blood droplet
will harden before the center
 Drip Trail Pattern: A pattern of bloodstains
formed by the dripping of blood of a moving
surface or person in a recognizable pathway
separate from other patterns
Interpreting Blood Stain Patterns
 Arterial Spatter: A characteristic blood stain
pattern containing spurts that result from
blood exiting under pressure from an arterial
 Expirated Blood Pattern: A pattern created by
blood that expelled out of the nose, mouth, or
respiratory system as a result of air pressure
and/or air flow
 Void: Something that takes the place of the
blood at a crime scene
Interpreting Blood Stain Patterns
 Transfer: A bloodstain pattern created
when a wet, bloody surface comes in
contact with a second surface.
 Low Velocity Spatter: Blood that falls at a
normal gravity speed, typically from an
open wound
 High Velocity Spatter: Blood that is flown
at a speed greater than that of gravity that
is associated with high-speed collisions,
such as gunshots or explosions
Interpreting Blood Stain Patterns
 Impact Spatter: a random pattern of
spatter of varying sizes
 Forward Spatter: Blood that travels
away from the source in the same
direction as the force that caused the
 Back Spatter: Blood directed back
toward the source of the force that
caused the spatter
What is Crime Scene
 The use of scientific methods,
physical evidence, deductive
reasoning and their interrelationships
to gain explicit knowledge of the
series of events that surround the
commission of a crime.
Who Participates In Crime Scene
 Reconstructing consists of the
 Medical Examiner
 Experienced Law Enforcement
 Criminalists
Steps of Crime Scene
 Recognition of evidence
 Documentation of evidence
 Collection of evidence
 Evaluation of evidence
 Hypothesis
 Testing
 Reconstruction
Crime Scene Reconstruction
 The criminalist must be prepared to answer the following
questions when examining dried blood
 Is it blood?
 From what species did the blood originate?
 If the blood is of human origin, how closely can it be associated
to a particular individual
 Detection of blood is best made by means of a preliminary
color test
Things To Consider At The Crime
 Origin(s) of bloodstain
 Distance of bloodstain from target
 Direction from which blood
Speed with which blood left source
Position of victim and assailant
Movement of victim and assailant
Number of blows/shots
Which type of blood?
 Once the stain has been
characterized as blood,
the precipitin test will
determine whether the
stain is of human or
animal origin
 Once the bloodstain
has been determined to
be of human origin, the
blood is typed
Test For Human Blood
Blood Group Characteristics
 Based on 2 glycolipid antigens (A & B) found on the surfaces
of RBC
Antigen A only= type A blood
Antigen B only= type B blood
Both antigens= type AB blood
No antigens= type O blood
Agglutination: the clumping together of red blood cells by the action of an antibody
Angle of Impact: acute or internal angle formed by the direction of a blood drop and the plane of
the surface it strikes
Antibody: a protein in the blood serum that destroys or inactivates a specific antigen
Antigen: a substance, usually a protein, which stimulates the body to produce antibodies against it
Anti-Serum: blood serum that contains specific antibodies
Area of Convergence: The area containing the intersections generated by lines drawn through
the long axes of individual stains that indicates in two dimensions the location of the blood source.
Area of Origin: the location of the blood source in 3-D perspective
Arterial Spray: Bloodstain pattern(s) resulting from blood exiting the body under pressure from a
breached artery
Back Spatter: A bloodstain pattern resulting from blood drops that traveled in the opposite
direction of the external force applied; associated with an entrance wound created by a projectile.
Blood Drops: gravity acts on the blood until it impacts a horizontal surface
Blood Smears :these happen when a bleeding person is moved
Blood Splashes: blood that has been thrown through the air until it struck a surface at angle
Glossary Cont.
Blood Spurts: this is result of arterial bleeding
Blood Trails: blood that is deposited when a wounded person walks or runs while dripping blood. It can
also happen from carrying or dragging a body
Drip Trail: A bloodstain pattern resulting from the movement of a source of drip stains between two
Forward Splatter: A bloodstain pattern resulting from blood drops that traveled in the same direction as
the impact force.
High-Velocity Impact Spatter: bloodstains resulting from blood with a velocity in excess of 100 ft per
Impact Spatter: A bloodstain pattern resulting from an object striking liquid blood.
Low-Velocity Impact Spatter: bloodstains resulting from blood with a velocity of 5 ft per sec or less
Luminal: a liquid that reacts to UV lighting and reveals that traces of blood
Medium Velocity Impact Spatter: bloodstains resulting from blood with a velocity of 5 ft to 25 ft per
Plasma: the liquid part of the blood
Pools of Blood: these pools are next to the body and may indicate if the body has been moved
Glossary Cont.
Satellite Spatter: A smaller bloodstain that originated during the formation of the parent stain as
a result of blood impacting a surface
Serology: the scientific study of blood
Skeletonization: A bloodstain consisting of a darkened peripheral rim where the center of the
stain is no longer intact.
Spattered Blood: a random distribution of bloodstains that vary in size that may be produced by a
variety of mechanisms
Transfer Patterns: A bloodstain resulting from contact between a blood-bearing surface and
another surface
Void: An absence of blood in an otherwise continuous bloodstain or bloodstain pattern.
Works Cited