1. A Brief review in
Blood Spatter Analysis
Ahmed Almumtin, MD
2. What does it remind you of?
• Forensic science?
• OR.. DEXTER!
3. Blood and Life
– Blood Volume
• On average, accounts for 8 % of total body weight
• 40% of total blood volume loss, externally or
internally is usually fatal ..
4. What is it?
• A field of forensic
examination of the shapes,
locations, and distribution
patterns of bloodstains, in
order to provide an
interpretation of the
physical events which gave
rise to their origin.
5. What does it tell us?
• 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
6. While a reconstruction could tell
some more..
1. Stain condition
2. Pattern
3. Distribution
4. Location
5. Directionality
7. Before that..
• Is it really blood? How to tell?
– a light source.
– Blood reagents: Phenolaphthalien (Kastle myer
test pink), HemaStix (tetramethylbenzedine Luminol
green or cyano with Hb) Reaction
– Luminol + UV light: (Blue)
• Can detect blood even if cleaned or
removed.
• Disadvantage: can give +ve results with
some metals ex. Copper, bleaching products
or paints.
– Flouroscine:
• Useful for fine smears or stains
8. Terminology
• Angle of impact: angle at which blood strikes a target surface
• Bloodstain transfer: when a bloody object comes into contact with a
surface and leaves a patterned blood image on the surfac
• Back-spatter: blood that is directed back toward the source of
energy
• Cast-off: blood that is thrown from an object in motion
• Directionality—relates to the direction a drop of blood travels in space
from its point of origin
• Contact stain: bloodstains caused by contact between a wet blood-bearing
surface and a second surface that may or may not have blood on it
Transfer—an image is recognisable and may be identifiable with a particular
object
Swipe—wet blood is transferred to a surface that did not have blood on it
Wipe—a non-blood-bearing object moves through a wet bloodstain, altering
the appearance of the original stain
9. • Parent Drop – The droplet from
which a satellite spatter originates.
• Satellite Spatters – Small drops Satellite Spatters
of blood that break of from the
Spines
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 Parent Drop
traveled.
10. Types of Blood stain patterns
• Passive Bloodstains (drops, pools, etc.)
• Transfer Bloodstains (wipe a weapon, etc.)
• Active (or “Projected”) Bloodstains (bullets,
stepping in blood, etc.)
12. Projected bloodstains
• Projected bloodstains are created when an exposed
blood source is subjected to an action or force,
greater than the force of gravity. (Internally or
Externally produced)
• The size, shape, and number of resulting stains
will depend, primarily, on the amount of force
utilized to strike the blood source.
13.
14. Arterial Spurt / Gush
• Bloodstain pattern(s) resulting from
blood exiting the body under pressure
from a breached artery:
15. Cast-off Stains
• Blood released or thrown from a blood-bearing object in motion
• A useful way to understand it, is to imagine yourself running
while holding a cup of pomegranate juice!
19. Droplets could be altered..
• Size of the droplet
• Angle of impact
• Velocity at which the blood droplet left its origin
• Height
• Texture of the target surface
• On clean glass or plastic—droplet will have smooth outside edges
• On a rough surface—will produce scalloping on the edges
20. Size and Velocity
• Low velocity spatter is about 5 ft / second
and usually 3 mm or greater in diameter and
indicates blood is dripping.
• Medium velocity spatter is 5 – 25 ft / second
with a <3 mm diameter and usually indicates
blunt trauma or sharp trauma or it could be
cast-off.
• High velocity spatter is 100+ ft / second with
a spatter of < 1 mm indicating gunshot
trauma, power tools, an object striking with
extreme velocity (airplane prop) or an
explosion, may be referred to as fly specks.
21. Impact
The more acute the angle of impact,
the more elongated the stain.
90-degree angles are perfectly round
drops; 80-degree angles take on
a more elliptical shape.
At about 30 degrees the stain will
begin to produce a tail.
The more acute the angle, the easier it is to determine the
direction of travel.
The shape of a blood drop:
Round—if it falls straight down at a 90-degree angle
Elliptical—blood droplets elongate as the angle decreases from 90 to 0
degrees; the angle can be determined by the following formula:
22. Surface and Shape
Medium impact occurs when a force Low impact is really blood under the
such as a bat is applied. influence of gravity - it just falls.
23. High impact - fine mist of droplets
Image
courtesy
Stuart
James,
February
2007
26. Stage 1: contact & collapse
Image used with permission from Tom Bevel & Ross Gardner, June 2006.
27. Stage 2: displacement
Image used with
permission from Tom
Bevel & Ross Gardner,
June 2006.
28. Stage 3: dispersion
Image used with permission
from Tom Bevel & Ross
Gardner, June 2006.
29. Stage 4: retraction
Image used with
permission from Tom Bevel
& Ross Gardner, June
2006.
30. Target surface texture
• Blood droplets that strike a hard smooth surface, like a piece of
glass, will have little or no distortion around the edge.
• Blood droplets that strike linoleum flooring take on a slightly
different appearance. Notice the distortion (scalloping) around the
edge of the blood droplets.
• Surfaces such as wood or concrete are distorted to a larger extent.
Notice the spines and secondary or sentinel spatter present.
•
31. Size or volume of droplets
• Large volumes of blood (patterns created by same volume of blood,
from same source to target distance)
"Dripped Blood" "Spilled Blood"
32. Impact Spatter
• Blood stain patterns created when a blood
source receives a blow or force resulting in
the random dispersion of smaller drops of
blood.
This category can be further subdivided
into;
Low Velocity
Gravitational pull up to 5 feet/sec.
Relatively large stains 4mm in size and
greater
33. Directionality
sin θ = W / L
What does W = L mean?
sin θ = 1 → θ = 90
Drop is a circle!
36. And from Dexter ;-)
• The common point, on a 2 dimensional surface, over which the directionality of
several bloodstains can be retraced.
• Once the directionality of a group of stains has been determined,
it's possible to determine a two dimensional point or area for the group of stains.
• By drawing a line through the long axis of a group of bloodstains the point of
convergence can be determined. Where the lines of the group of stains intersect
one another the convergence point can be established.
37. Continue Directionality
• When considering the shape of a blood stain for use in
calculating its angle of impact, only a sharp, well-defined
blood stain should be used for measuring its width and
length
• Directionality of a blood drop while in flight is usually
obvious from the geometry of its resulting blood stain
– The pointed end indicates direction of travel of the drop
prior to impact on a surface
– Direction of travel may also be determined when edge
scallops only appear on one side of the stain
38.
39. • A few blood stains do not make a pattern
• Draw conclusions with reservations and/or qualifications
• It is ok to admit that there is insufficient evidence to draw
a conclusion from BPA
• No opinion is better than an incorrect, forced opinion
40.
41.
42. • When the preponderance of individual
bloodstain diameters are less than 1mm,
they are consistent with having been
produced as the result of high velocity
impact (most often shooting)
43. • When the preponderance of individual
bloodstains are 1mm or more in diameter,
they are consistent with having been
produced as the result of medium velocity
impact (most often beating or stabbing)
44. • The shape of a bloodstain is a function of
the angle at which it hits/impacts the surface
• Perfectly roundninety-degree impact/drop
angle
• Angle of impact of elliptical drop may be
determined using length to width ratio of
the drop
