It is the interpretation of bloodstains at a crime scene in order to recreate the actions that caused the bloodshed. Analysts examine the size, shape, distribution and location of the bloodstains to form opinions about what did or did not happen.
2. INTRODUCTION
Blood spatter analysis /blood spatter interpretation is the evaluation of the size,
shape and distribution of patterns that are identified in blood.
The purpose is to possibly identify the activities that took place to deposit the
blood and also possible to identify the location of the individual during the
bloodshed.
The first step is to identify the basic patterns.
By identifying patterns ,conclusions can be drawn about what type of activity
took place to create those patterns.
These are recognizable patterns and they are reproducible patterns.
Blood stain interpretation is a part of overall investigation,which
includes documentation,collection and evaluation of all physical evidence.
The information provided by the blood stain interpretation is evaluated in
conjunction with evidence provided by the post mortem examination of
victim and analyses performed by crime laboratory.
3. The information is obtained from blood by the forensic pathologist ,toxicologist
,serologist and crime scene investigator.
Bloodstain pattern interpretation uses sciences-biology,physics and mathematics.
FORENSIC PATHOLOGIST
Blood is studied by forensic pathologist to assist with diagnosis of various
diseases that may relate to the death.
The degree of postmortem lividity or settling of blood within the body may help to
establish the approximate time of death or whether the lividity is consistent with the
position of victim at the crime scene.
CHERRY RED LIVIDITY –carbon monoxide poisoningcyanide poisoning.
Blunt trauma –contusionsexternal bruising-freshold
Petechiae-minute hemorrhages in eye asphyxial death.
4. • FORENSICTOXICOLOGIST
To determine the presence or absence of alcohols,drugs and poisons.
Quantative blood level of toxic agents helps to establish the cause and
manner of death or provide evidence of an intoxicated driver.
Interpretation of toxicological data -diagnosis of drug and alcohol abuse or
assist with explanation of erratic behavior of individuals who may injure
themselves or other persons.
FORENSIC SEROLOGIST
Establishes the presence of blood
Distinguishes human from animal blood.
To establish identity of blood -to whom it belongs-victim/suspect.
ABO grouping /other antigenic systems/isoenzyme systems/DNA
typing/other individualization systems.
5. RECONSTRUCTION OF A CRIME SCENE
Blood stains studied –in respect to their goemetry –distribution on various surfaces –reveal
valuable information –reconstruction of events-that produced the bloodshed.
Orgin of bloodstains
Distance between target surface and orgin at time of bloodshed
Type and direction of impact that produced bloodstains
Objects that produced particular blood stains
Number of blows,shots,etc.that occurred.
Position ,/movemen/direction of victim,assailant or objects during bloodshed /after
bloodshed
Support /contradicion of versions of events by suspects/witneses
Additional critirea for estimation of time of death
Correlation with other laboaories and pathology findings relevant to an investigation
6. HISTORIC DEVELOPMENT
PRE-HISTORIC
MAN
•TO TRACT WOUNDED ANIMALS ,HUNTING.
19th CENTURY
•GERMAN FORENSIC CHEMIST-PAUL JESERICH
•USE OF BLOODSTAIN INTERPRETATION IN CRIMINAL INVESTIGATIONS
1939
•FRENCH SCIENTIST –BALTHAZARD
•TREATISE OF BLOODSTAIN PATTERN EXPERIMENTS-22nd CONGESS OF FORENSIC MEDCINE IN PARIS,FRANCE
1955
•CRIMINALIST-PAUL KIRK ,BERKELEY,CALIFORNIA.
•SIGNIFICANT MILESTONE-RECOGNITION OF BLOODSTAIN EVIDENCE IN LEGAL SYSTEM
•SUCCESSFULLY USED-BLOODSTAIN EVIDENCE CASE OF OHIO vs SAMUEL SHEPPARD
1971
•HERBERT LEON MACDONNEL,CORNING,NEW YORK
•CONDUCTED EXPERIMENTS TO RE-CREATE AND DUPLICATE BLOODSTAIND OBSERVED IN CRIME SCENES
•FIRST MODERN TREATISE TITLED-"FLIGHT CHARACTERISTICS AND STAIN PATTERNS OF HUMAN BLOOD.
1983
•INTERNATIONAL ASSOCIATION OF BLOODSTAIN PATTERN ANALYSTS
1999
• FBI –CRITICAL REVISION OF [PRESUMPTIVE TESTS FOR BLOOD STAINS.
•BY PONCE AND VERDUPASCUAL ( FORENSIC SCIENCE COMMUNICATIONS,JULY199)
7. PROPERTIES OF BLOOD
• FLUID-consisting cellular compoents and plasma
• Circulates through arterial and venous systems of the body
• Colour of blood –presence of oxygenated hemoglobin in red cells
• Arterial blood-brighter red-high levels of oxyhemoglobin
• Less in venous system –due to distribution of oxygen and return of co2 to the
lungs.
• Due to a trauma or disease ,when blood exposed to external environment -
subjected to various forces – behave in predictable manner -based on laws of
biology,physics and mathematics.
• Biologically-clotting and drying procees will be intiated.
-observations of degree of clotting / serum production/extend of drying of blood
-helps to estimate time since blood shed.
8. • PHYSICALLY -Blood being a liquid-behaves according to laws of fluid
dynamics.
• Its physically properties -vicosity, specific gravity,surface tension ,forces
acting on blood outside the body -determine the size ,shape ,directionality and
location of bloodstains on various surfaces.
• Experiments have confirmed that blood follows the principle of fluids in
motion.
• Blood droplets are formed-small masses of liquid seperates from a larger mass
outside the body.
• Seperation of these drops from source is caused by gravity/impact to the blood
source exceeding the forces of surface tension(molecular cohesive forces that
causes the surface of a liquid to resist peneteration and seperation) and
viscosity (resistance of a fluid to flow/to change form/position of molecules –
due to attraction of molecules to each other.) of the blood.
9. A DROP OF BLOOD
• The average volume of a drop of blood is approximately 0.05 ml
• Experiments have shown that –volume of drop varies from approximately,0.01-0.16 ml
–when allowed to drip from various surfaces.
• Terminal velocity /maximum speed of a free falling drop acheved when acceleraion of
drop –offset by resistance of air
• Macdonnel-established that for –A drop size approximately 0.05ml ,terminal velocity is
25+- 0.5 feet/second.
• Smaller drop volumes-lower terminal velocities
• Larger drop of volumes-higher terminal velocities
• Macdonnel –demonstrated-sinle drop of blood will not break up into smaller droplets
by simply falling through air; for this to occur the drop must either strike an
object/acted upon by a additional force.
10. PROPERTIES BLOOD STAINS
• A blood droplet striking a surface at 90 degree – produce a bloodstain which
is essentially circular in shape.
• A blood droplet striking at less than 90 degree- elongated /oval shaped
blood stains.
• The shape of blood droplet formed is independent of forces acting upon blood
sources(gravity/impact to exposed sorce of blood)
• The force factors will affect size not shape of resultant blood stains
• Bloodstain on rough textured surface- spines & peripheral spatter(due to
disruption in surface tension of blood droplet caused upon impact.
• Blood stain in smooth/hard surfaces-will only show little distortion if any.
11. • The size /diameter of blood stains –increases with distance from which it has
fallen-upto about 7 feet.
• Beyond 7 feet – the diameter does not increase.
• Diameter range from 13 to 22 mm.
• Estimation of distance from which a blood drop has fallen-based upon
diameter of blooddrop-must also take into account the volume
of original blooddrop, which may be unknown.
12. • Volume projected blood- more than 1.0 ml of blood –projected –in manner
exceeding gravitational forces & low velocity impact-result in streaking
elongated peripheral spatters. E. g; vomiting of blood.
• Arterial gushing /spurting- show large stains with downward flow patterns on
vertical surfaces/ smaller discrete stains of uniform size.-if victim close to the
floor- produce large pool of blood on the floor.
• Cast off patterns- uniformly distributed trails-more elongated stains distant
from the source.
• Generally in –4 to 8 mm range -cast off stains.
• Type of weapon/amount of blood adhering /length of arc of the swing-
produce small/large stains.
• Determination of angle of impact, point of convergence-will give position of
assailant swinging the weapon
• Number of distinct trails of cast-off bloodstains –to estimate minimum
number of blows struck.
13. • FLOW PATTERNS
Indicate the direction of travel of blood moving horizontally/vertically on
surfaces due to gravity.
Directional changes occur due to objects in path of the blood flow/changes in
surface angles/alterations of position of sources of blood.
Flow patterns-bleeding source-pool of blood.
SMUDGE
• Bloodstain that has been altered/distorted by contact with a non-bloody
surface.
DENSE ZONES
The lower area or base of bloodstain will be denser (gravitatinal force)due to
continued accumulation of blood due to gravity when a blood droplet strikes
non horizontal surface .
14. • ANGLE OF IMPACT
• Angle of impact is defined as the internal angle
at which a blood strikes a target surface.
• Angle of impact -function of relationship
between width and length of resultant bloodstain.
• At an angle of 90 ,-circular stai with equal width
and length.
• More acut the angle of impact- the greater the
elongation of bloodstain
• Measurement of width and length-
taken through central axis of each dimension.
• The calculated value of W/L ratio is used in
formula;
Angle of impact = arc sin W/L
Arc sin – inverse function of sine,
It returns the angle whose sine is a given number
15. • POINTS OF
CONVERGENCE
• A point of convergence – common
point to which individual bloodstains
in a pattern can be traced or
projected on a surface.
• Determined by tracing the long axis
of well defined blood stains back
to two-dimensional common point or
points .
• Can be accomplished ina crime scene
by use of strngs extending
through long axis of blood stains.
• Point of convergence can be
represented graphically by
measuring the location of
the bloodstains and angles of
directionality relative to known sets
of prints.
16. POINT OF ORIGIN
• The point of origin is defined as the location in space from which the
blood that produced bloodstain originated.
• It is determined by projecting calculated angles of impact of well-
defined bloodstains back to an axis constructed through point of
convergence.
• It as 3-dimensional representation in space.
• Semi-protractor and string -used to construct point of origin in scene
• Can also be plotted graphically-by plotting the distance of the individual
bloodstains from point of convergence with their angle of impact.
• Point of origin may represent the distance from a wall, ceiling or other
structure.
17. • Four methods can be used to
determine point of origin of blood
source
Graphical method
Tangent method
String line method
Computer assisted methods
18. COMPUTER SOFTWARES
• Computer programs exist to process the data obtained from the measurement
of blood stains for the determination of convergences and point of origin – they
do not replace the need for accurate measurements of the bloodstains.
• STAINER 1.0 SOFTWARE –forensic solutions of Nashville, tennesse –provide
automated calculations of all necessary distances with measurements from at
least two bloodstains with a common origin.
• Current version of program is designed for use on IBM PC-COMPATIBLE
SYSTEMS using MS-DOS operating systems.
• Currently, bloodstain experts use a computer program called BackTrack to
determine the origin of a bloodstain pattern.
• Using Directional Analysis, the BackTrack™ suite of computer programs can be
used to analyze a crime scene in which bloodstains only from downward-
moving drops are available. It is a specialized Linux distribution
19. TYPES OF BLOOD STAINS
Bloodstains are classified into three basic types: passive stains, transfer stains
and projected or impact stains.
Passive stains include drops, flows and pools, and typically result from gravity
acting on an injured body.
Transfer stains result from objects coming into contact with existing bloodstains
and leaving wipes, swipes or pattern transfers behind such as a bloody shoe print
or a smear from a body being dragged.
Impact stains result from blood projecting through the air and are usually seen as
spatter, but may also include gushes, splashes and arterial spurts.
BLOOD SPATTER
Blood spatter is categorized as impact spatter (created when a force is applied
to a liquid blood source) or projection spatter (caused by arterial spurting,
expirated spray or spatter cast off an object).The characteristics of blood spatter
depend on the speed at which the blood leaves the body and the type of force
applied to the blood source.
20. • Gunshot spatter - includes both forward spatter
from the exit wound and back spatter from the
entrance wound. Gunshot spatter will vary
depending on the caliber of the gun, where the
victim is struck, whether the bullet exits the body,
distance between the victim and the gun and
location of the victim relative to walls, floors and
objects.Typically, forward spatter is a fine mist and
back spatter is larger and fewer drops.
• Cast-off - results when an object swung in an arc
flings blood onto nearby surfaces.This occurs when
an assailant swings the bloodstained object back
before inflicting another blow.Analysts can tell the
direction of the impacting object by the shape of the
spatter (tails point in the direction of motion).
Counting the arcs can also show the minimum
number of blows delivered.
21. • Arterial spray - refers to the spurt of blood released when a major artery is severed(
arterial gushing/spurting). The blood is propelled out of the breached blood vessel
by the pumping of the heart and often forms an arcing pattern consisting of large,
individual stains, with a new pattern created for each time the heart pumps.
• Expirated spatter - is usually caused by blood from an internal injury mixing with
air from the lungs being expelled through the nose, mouth or an injury to the
airways or lungs. Expirated spatter tends to form a very fine mist due to the
pressure exerted by the lungs moving air out of the body. Small air bubbles in the
drops of blood are typically found in this type of spatter.
22. CLASSIFICATION OF BLOODSTAIN
PATTERNS
• Blood stains are characterized by their appearance on various surfaces-blood
contacts on subsequent to bloodshed.
• The forces acting on blood exiting from the body forms the basis for
classification of blood stains
GENERAL
CATEGORIES
LOWVELOCITY
BLOODSTAIN
PATTERNS
MEDIUM-
VELOCITY
BLOODSTAIN
PATTERNS
HIGHVELOCITY
BLOOD STAIN
PATTERNS
23. LOW VELOCITY BLOOD STAINS
• Greatest variety of shapes and sizes –usually longer
than those produced by medium and high velocity
impact.
• When impact force is 5 feet/second or less.(low-
velocity force)-is considered as low velocity impact
stains. the bloodstain size is 3mm and larger.
• Individual drops of blood -from source of blood -
subjected to only gravity .
• Free falling drops –produce elongated blood stains-
when subjected to horizontal force of motion. e.g; a
person walking / running while dripping blood from
object or a wound.
• Drip patterns –drops of blood falling into previously
deposited wet blood on surfaces.
• Dripping blood often falls at a 90-degree angle and
forms a 360-degree (circular) stain when it hits a flat
surface.
24. MEDIUMVELOCITY BLOOD
STAINS
• Blood stain produced on a surface – subjected to a force – 5 to 25
feet/second upto 100 ft/sec .
• Energy impact causes blood to be broken into blood droplets.
• Blood droplets produced in the range of 1 to 4 mm .
• Blows with a blunt object as well as sharp objects wil produce medium velocity
stains
• Blood droplets radially radiated away from impact site .
• Events other than beating can produce medium velocity
blood stains examples:coughing and expiration of blood through mouth and
nos ,minor events such as slapping of hand /object as well as fly activity.
• Fly activity –for proper interpretation of blood spatter.
25. ALTERED BLOODSTAINS
• COMMON HOUSEFLY- mouth parts specilalized for
lapping and sucking –horsefly characterized as bitter.
• MOSQUITO-pecialized for piercing and sucking.
• Flies ingest and regurgitate it to a surface.
• Surface may show evidence of
excretion defecation,partly digested blood.
• The bloodspatter produced- in mm or less in size with
no definite point of origin.
• It can be seen on many surfaces such as decomposing
body and clothing.
• Coclusion taken must be conservative and
carefully considered ,especially when limited number
ofstains are only available.
26. HIGH VELOCITY
BLOODSTAIN PATTERNS
• It is prodduced by high velocity force striking a source of blood.
• Approximately 100 ft/second or more-associated with gunshot residue and
high speed machinery.
• Mist-like dispersion of minute blood droplets is a characterstic feature.
• Due to low mass of these droplets-limited distance travelled in space(approx-
3-4 feet)
• Resultant droplets with diameter of 0.1 or less.
• Mostly associated with gunshot injury- blood spatter may originate
from entrance /exit wound.
• Spatter from entrance wound-back spatter-travel opp to direction of projectile
toward weapon and shooter.- mostly associated with close-range discharge of
firearm- blood spatter on firearm-chest of shooter ,hand and arm.
27. • Forward spatter-associated with an exit wound-blood droplets travelling in
same direction-as projectile-More quantity than back spatter.
• Determination of point of origin-assists with position of victim and assailant
at time of discharge of weapon and intial bloodshed.
