What is forensic science?
• Forensic Science is the application of
science to the law.
• It often involves police officers and
scientists from many branches of science
working as a team to solve a crime.
How did Forensic Science catch
their killer?
How did Forensic Science catch
their killer?
1. Why do you think it is important that
‘Most forensic scientists are not police
officers’?
2. The evidence in this case was collected
from 4 major sites – can you name
them?
3. How long did it take the Forensic
Science Service to process all the
evidence?
Investigating Blood
Spatter Patterns
Categories of blood stains
• Blood patters can be roughly grouped into
3 categories:
• Passive
• Transfer
• Projected
Passive
These are drops created only by the force of
gravity.
They can be further
subdivided into
•Drops
•Drip patterns
•Pools
•Clots
Transfer
• These occur when a wet, bloody surface
contacts another surface. This may lead to
a recognisable footprint or
hand/fingerprint.
Projected
• This is where the source of bleeding is
subjected to another force – e.g. a blow or
sudden movement. The size and shape of
the drops produced depends on the size of
the force.
What else can affect the patterns?
•
•
•
•
The amount of blood
The surface it lands on
The height it drops from
The direction it comes from
Blood on glass – no
distortion
Blood on
linoleum –
distortion of
edges
Blood on wood – lots of
distortion
Types of Blood Spatter
• Low velocity (1.5 m/s)
– e.g. free-falling drops, cast off from
weapon
• Medium velocity (7.5 - 30 m/s)
– e.g. baseball bat blows
• High velocity (>30 m/s)
– e.g. gunshot, machinery
Investigating blood patterns
• Your task is to carry out an investigation to
see if the height that blood drips from
(passive) affects how big the droplets are.
Blood patterns results
Height (M)
Size of drop
(mm)
Size of drop Average size
(mm)
of drop (mm)
What is Forensic Science all
about?
•
•
•
•
•
•
•
Anthropology
Ballistics
Crime
Entomology
Evidence
Fibres
Trace
•
•
•
•
•
•
•
Fingerprints
Odontology
Insects
Serology
Toxicology
Pathology
All about SCIENCE!
Blood Spatter Analysis –
extension higher ability
CSI
The origin is in the angle
History
• 1894 - Pitorowski wrote earliest reference to bloodstain
pattern analysis
• 1939 - Balthazard was first to use physical
interpretations of stains
• 1955 - Dr. Paul Kirk used 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
Summary




What is Blood?
Determining Distance of Blood
Determining Direction of Blood
Types of Blood Stain Patterns
What is Blood?
Introduction to Blood
Blood Spatter (or splatter)
Blood drops form different shapes and sizes
Blood spatter analysis uses the shapes
and sizes to reconstruct the crime scene.
Blood Spatter > Distance
Determining Distance Blood Falls
Blood drops fall as small spheres
Blood Spatter > Distance
Determining Distance Blood Falls


Drops form circle when hitting surface
Size depends on speed of blood drop
Blood Spatter > Distance
Determining Distance Blood Falls
Faster drop = larger diameter (size)
Higher distance = larger diameter
Due to air resistance, speed maxes out at
distances above about 7 feet
Blood Spatter > Distance
Determining Distance Blood Falls
However, size of drop also depends on the
volume of the drop.
Volume depends on the object blood
originated from (needle = small; bat = large).
Blood Spatter > Distance
Determining Distance Blood Falls
Since the volume of blood is unknown…
The distance a drop has fallen
cannot be measured.
Blood Spatter
Effect of Surface


Smooth surface = smooth sphere
Rough surface may cause some splatter
Blood Spatter > Direction
Determining Direction of Blood
Narrow end of a blood drop will point in
the direction of travel.
Activity - 1
• Obtain the blood solution, dropper, protractor
and paper plate
• Drop one drop of blood from 3 feet above the
plate with the plate at 90 degrees to the dropper
(i.e. 0 degrees on the protractor)
• Drop 3 more drops in different locations but with
each subsequent drop decrease the angle
between the dropper and the plate and either
take a picture or draw what you see
• Record the angles used and observe the drops
• Describe what you see
Angle
(degrees)
Picture (Drawn or photographed) Picture observations
90 (0 on
protractor)
Insert photo or drawing
Describe in detail what you
see
60 (30 on a
protractor)
Insert photo or drawing
Describe in detail what you
see
30 (60 on a
protractor)
Insert photo or drawing
Describe in detail what you
see
10 (80 on a
protractor)
Insert photo or drawing
Describe in detail what you
see
Conclusion
• Describe the relationship of angle of
surface to blood pattern observed
• So angle angle of impact can be
determined
Angle of Impact
“The tail tells the tale”
• 90 degrees –
• 60 degrees –
• 30 degrees –
• 10 degrees –
Blood Spatter > Direction
Determining Direction of Blood
If more than one drop (from spatter)
results, the point of origin can be
determined
Blood Spatter > Direction
Determining Direction of Blood
If more than one drop (from spatter)
results, the point of origin can be
determined
Blood Spatter > Direction
Determining Direction of Blood
This is a 2-dimensional point of origin.
It is possible to determine the 3-D point of origin
Blood Spatter > Direction
Determining Direction of Blood



The angle can be determined
mathematically.
Width/Length, then take the
inverse sin (sin-1).
This number is the impact
angle (90 = perpendicular to
surface; <10 at a sharp angle)
Blood Spatter > Direction
For each blood
drop, a string can
be guided back to
the point of
origin.
Activity 2 3D blood splatter
• Determine the 3D angle of our blood
spattered wall and the position of our
victim
Blood Spatter
Types of Spatter

Spattered Blood = random distribution of
bloodstains that vary in size

Amount of blood and amount of force
affect the size of blood spatter.

Can result from gunshot, stabbing,
beating
Blood Spatter
Spattered Blood can:

Help determine the location of the origin
of the blood source.

Help determine the mechanism which
created the pattern.
Blood Spatter
Spattered Blood
In general, for higher impacts, the pattern
is more spread out and the individual
stains are smaller.
Low impact = beating
High impact = gunshot
Blood Spatter
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.
Blood Spatter
Gunshot Spatter
Gunshots result in back spatter
(where bullet enters) and
forward spatter (where bullet
exits).
Blood Spatter
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.
Blood Spatter
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.
Blood Spatter
Types of Spatter
Castoff Pattern = Blood flung off of
swinging object.
Can reconstruct where assailant and victim
were positioned.
Blood Spatter
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.
Blood Spatter
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.
Activity 3
• Blood analysis website
• Try to recreate some of these blood
splatter patterns on A5 paper after reading
through the website (without injuring any
one please!!!!)
• You must consult your teacher when about
to begin to ensure your safety