Forensic Science Lab Activity
Warning: Some material in this presentation and
related videos may be too graphic for some people.
Blood Spatter Analysis
Blood drops form different shapes and sizes
Blood spatter analysis uses the shapes and
sizes to reconstruct the crime scene.
This is How Hollywood Interprets
Blood Spatter Analysis:
Formation of Blood Spatter:
History
• 1894 - Pitorowski wrote earliest reference to bloodstain
pattern analysis.
• 1939 - Balthazard was first to use physical
interpretations of stains.
• 1955 - Dr. Paul Kirkused bloodstain pattern interpretation
as a defense witness in the Sam Shepherd case.
• 1971 - Professor Herbert MacDonnell promoted
bloodstain pattern interpretation as a tool for modern
criminalistics.
• 1983 – The International Association of Bloodstain
Pattern Analysis was formed.
What does the abbreviation BPA represent?
Bloodstain Pattern Analysis
What can an investigator learn from the
analysis of a blood spatter?
 Type and velocity of weapon
 Number of blows
 Handedness of assailant (right or left-handed)
 Position and movements of the victim and
assailant during and after the attack
 Which wounds were inflicted first
 Type of injuries
 How long ago the crime was committed
 Whether death was immediate or delayed
How is blood evidence detected at a crime scene?
Light Source
Investigators will first examine
the crime scene to look for areas
that may contain blood. They
may use a high-intensity light or
UV lights to help them find
traces of blood as well as other
bodily fluids that are not visible
under normal lighting conditions.
How is blood evidence detected at a crime scene?
Blood Reagent Tests
These tests, referred to as presumptive tests,
are used to detect blood at crime scenes based
upon the properties of hemoglobin in the
blood. Further tests at the crime lab must be
done to verify that it is human blood.
Examples:
• Kastle-Meyer test.
•HemaStix is a strip that has been coated with
tetramethylbenzidine (TMB) and will produce
a green or blue-green color with the presence
of hemoglobin.
The Kastle-Meyer test is
• a presumptive blood test, first
described in 1903, in which the
chemical indicator phenolphthalein
is used to detect the possible
presence of hemoglobin. It relies on
the peroxidase-like activity of
hemoglobin in blood to catalyze the
oxidation of phenolphthalin (the
colorless reduced form of
phenolphthalein) into
phenolphthalein, which is visible as
a bright pink color
Kastle-Meyer Test
Luminol / Blue Star
This chemical is used by crime scene
investigators to locate traces of blood, even if
it has been cleaned or removed.
Investigators spray a luminol solution is
throughout the area under investigation and
look for reactions with the iron present in
blood, which causes a blue luminescence.
One problem is that other substances also
react, such as some metals, paints, cleaning
products, and plant materials. Another problem
is that the chemical reaction can destroy other
evidence in the crime scene.
Luminol Reaction
Fluorescein
This chemical is also capable of detecting latent
or old blood, similar to luminol. It is ideal for
fine stains or smears found throughout a crime
scene. After the solution has been sprayed onto
the substance or area suspected to contain blood,
a UV light and goggles are used to detect any
illuminated areas, which appear greenish-white
if blood is present. It may also react to many of
the same things as luminol (copper and bleach).
Fluorescein Reaction in
UV Light
LCV or Leuco Crystal Violet, is one type of chemical
process that is used for blood enhancement. Using this test
helps to make the blood evidence more visible so it can be
photographed and analyzed.
Blood Pattern Analysis
•
•
The use of physics and math to interpret
bloodstain patterns within a forensic
setting
May show:
1.
2.
3.
4.
5.
Activity at scene
Number of blows
Position of victim and assailant
Whether death was immediate or delayed
Weapon characteristics
Bloodstain Pattern Analysis Terms
• Spatter – Bloodstains created from the application of force to the area
where the blood originated.
• Origin/Source – The place from where the blood spatter came from or
originated.
• Angle of Impact – The angle at which a blood droplet strikes a surface.
• Parent Drop – The droplet from which a
satellite spatter originates.
• Satellite Spatters – Small drops of blood that
break of from the parent spatter when the blood
droplet hits a surface.
• Spines – The pointed edges of a stain that
radiate out from the spatter; can help determine
the direction from which the blood traveled.
Satellite Spatters
Spines
Parent Drop
Basic Principles
•
•
A free falling drop of
blood forms a sphere or
ball.
A spherical drop will
break
1. When it strikes another
object
2. When acted upon by
some force
Types of Bloodstain Patterns
• Passive Bloodstains
– Patterns created from the force of
gravity.
– Drop, series of drops, flow patterns,
blood pools, etc.
Types of Spatter
Satellite Spatter = free falling drops of blood
that fall onto a spatter pattern.
 These drips are usually much larger than
impact spatter.
 However, blood dripping into blood can
create a spatter.
Types of Bloodstain Patterns
• Projected Bloodstains
– Patterns that occur when a force
is applied to the source of the
blood
– Includes low, medium, or high
impact
spatters,
cast-off,
arterial spurting, expiratory
blood blown out of the nose,
mouth, or wound.
Types of Spatter
Gunshot Spatter = can result in a mist-like
spatter that indicates a gunshot.

Not all gunshots will result in misting.

If misting is present, it is most likely a
gunshot.
Gunshot Spatter
Gunshots result in back spatter
(where bullet enters) and forward
spatter (where bullet exits).
Types of Spatter
Beating and Stabbing Spatter = larger
individual stains
First blow usually doesn’t result in spatter
since there is not yet any exposed blood.
Arterial Gushing
Arterial Spray (Gushing)
Types of Spatter
Castoff Pattern = Blood flung off of
swinging object.
Can reconstruct where assailant and victim
were positioned.
Cast-off Bloodstains
Cast Off
More Cast Off
Types of Spatter
Expirated Bloodstain Pattern = Blood can
accumulate in lungs, sinuses, and airway.
Forcibly exhaled.

Can appear like beating or gunshot pattern.

May be mixed with saliva or nasal
secretions.
Types of Bloodstain Patterns
• Transfer or Contact Bloodstains
– These patterns are created when a wet,
bloody object comes in contact with a
target surface; may be used to identify
an object or body part.
– A wipe pattern is created from an
object moving through a bloodstain,
while a swipe pattern is created from
an object leaving a bloodstain.
Other Patterns in Blood
• Transfer patterns (gun, knife, hand, foot…)
• Void patterns (indicating some object was
removed or a person was hit by spatter)
• Flow patterns (may indicate movement
with change in flow)
Void
Drying Time
•
•
Drying begins at periphery and proceeds
inward
Drying time is affected by
–
–
–
•
Surface type
Amount of blood
Climatic conditions
Skeletonization
–
–
Partially dry stains leave a ring that outlines original
spatter
The drier the stain, the less skeletonization shown
Clotting Time
• Clotting time outside the body ranges from
3 – 15 minutes
• Spattered clots indicate that time passed
between the initial bleeding and later
blows
• Coughing of clotted blood may indicate
post-injury survival of victim
Alteration of bloodstain over time



Blood dries and clots over time.
Difficult to estimate the time the blood exited
the body.
Clotted smears can indicate time of movement.
Blood Spatter > Distance
Determining Distance Blood Falls
Slower drop = larger diameter (size)
Higher distance = larger diameter
Due to air resistance, speed maxes out at
distances above about 7 feet
Spatter size is dependent upon velocity
•
Low velocity:
–
–
–
•
Speed = about 5 ft/second.
Usually 3 mm or greater in diameter.
Indicates blood is dripping.
Medium velocity:
–
–
–
•
Speed = 6 – 25 ft/second.
Between 1 - 3 mm in diameter.
Usually indicates blunt trauma, sharp trauma or cast-off.
High velocity:
–
–
–
–
Speed = 100+ ft/second.
Less than 1 mm in diameter.
Indicating gunshot trauma, power tools, an object striking with
extreme velocity (airplane prop) or an explosion.
May be referred to as fly specks.
Determining Distance Blood Falls
•
•
Size depends on speed of blood drop.
However, size of drop also depends on
the volume of the drop.
Volume depends on the object blood
originated from (needle = small; bat = large).
Effect of Surface


Smooth surface = smooth sphere
Rough surface may cause some splatter
Determining Location of Blood Source
•
Direction of travel:
–
•
tail will point in direction of travel.
Angle of impact:
–
–
Vertical drops are circular.
Drop elongates as angle increases.
Determining Direction of Blood
Narrow end of a blood drop will point in the
direction of travel.
Determining Direction of Blood
If more than one drop results from a spatter,
the point of origin can be determined
For each blood
drop, a string can
be guided back to
the point of origin.
Angle of Impact
Angle of Impact
“The tail tells the tale”
• 90 degrees –
• 60 degrees –
• 30 degrees –
• 10 degrees –
Shapes of spatter are affected
by angle of motion:
Angle of Impact
• Measure the width and the length (excluding
tail) of the stain/spatter.
• sine=
width
=
9mm
length
=
18mm
(9 divided by 18 = 0.500)
.500 = Angle of 30 Degrees
Angle
0°
sin
.000
cos
tan
cot
sec
csc
1.000
.000
Undefined
1.000
Undefined
.
26°
.438
.899
.488
2.050
1.113
2.281
27°
.454
.891
.510
1.963
1.122
2.203
28°
.469
.883
.532
1.881
1.133
2.130
29°
.485
.875
.554
1.804
1.143
2.063
30°
.500
.866
.577
1.732
1.155
2.000
31°
.515
.857
.601
1.664
1.167
1.942
32°
.530
.848
.625
1.600
1.179
1.887
33°
.545
.839
.649
1.540
1.192
1.836
34°
.559
.829
.675
1.483
1.206
1.788
35°
.574
.819
.700
1.428
1.221
1.743
36°
.588
.809
.727
1.376
1.236
1.701
37°
.602
.799
.754
1.327
1.252
1.662
Calculated point of origin
• Closer for high velocity spatter or when
stains originate closer to where the spatter
occurred.
Point and area of
convergence
• To determine the point/area of convergence an
analyst has to determine the path the blood
droplets travelled. The tangential flight path of
individual droplets can be determined by using
the angle of impact and the offset angle of the
resulting bloodstain.
• “Stringing” stains is a method
of visualizing this.
– For the purpose of the point of
convergence, only the top view of
the flight paths is required. This is
a two-dimensional (2D) - not a
3D intersection.
• The point of convergence is
the intersection of two
bloodstain paths, where the
stains come from opposite
sides of the impact pattern.
String Convergence in a 2 Dimensional Plane
Convergence
• The area of convergence is the box formed
by the intersection of several stains from
opposite sides of the impact pattern.
The Area of Origin
• The area in 3dimensional space
where the blood
source was located at
the time of the
bloodletting incident. It
includes the area of
convergence with a
third dimension on the
z axis, which is
perpendicular to the
floor.