Warm-Up
November 14, 2014
• What are the different blood types?
• What are ways to detect blood at a crime
scene?
Objective
• SWBAT analyze blood spatter.
Agenda
1.
2.
3.
4.
5.
Blood Typing Lab
Grave Evidence Documentary
Bloodstain Patterns
Blood Spatter Lab
Forensic Files Friday
Forensic Science
Blood Typing Lab Activity
T. Trimpe 2006 http://sciencespot.net/
The Crime Report
A small pool of blood and a weapon was found near a
garbage dumpster. After examining the area, the CSI
on the scene discovered a body in the garbage
dumpster and identified him as Earnest “One-Eyed”
Earl. Earl had a wound to his chest that will be
analyzed by the medical examiner.
The CSI tested blood samples from the blood pool
and the weapon at the crime scene. It was determined
that it was human blood, but he needs to know the
blood type to help identify if it was from the victim or
the person who murdered him. He has come up with
three suspects that either knew the victim or were
seen in the area before the body was discovered. He
would like to question them further while he waits for
DNA test results.
Follow your teacher’s directions to complete the lab.
Remember to be careful to prevent cross-contamination of the blood samples!
Image: http://www.fbi.gov/publications/leb/2005/apr2005/apr2005leb_img_3.jpg
Blood Typing Test
We will be determining blood types using Anti-A
serum, Anti-B serum, and Anti-RH serum. Use
the chart to help you determine the blood type of
each sample and its Rh factor (+ or -).
Type
Reaction w/
Anti-A Serum
Reaction w/
Anti-B Serum
A
+
-
B
-
+
AB
+
+
O
-
-
Clumping = + (Positive)
No Clumping = - (Negative)
Rh Serum - Clumping = Rh+ blood
DIRECTIONS:
Step 1: Label the three cups in your kit as Anti-A, Anti-B, and Anti-Rh.
Step 2: Place 20 drops of the blood sample in each cup.
Step 3: Place 10 drops of the anti-A serum in the A cup.
Step 4: Place 10 drops of the anti-B serum in the B cup.
Step 5: Place 10 drops of the anti-Rh serum in the Rh cup.
Step 6: Use a clean toothpick for each sample and stir for 30 seconds.
Step 7: Record your observations in the correct section on the back of the page and use the
reaction chart at the top of this page to determine the blood type.
Step 8: Complete the other sections using information from your classmates.
Clumping =
Positive Result
Agglutination = Clumping = Positive Reaction
Type
Reaction w/
Anti-A Serum
Reaction w/
Anti-B Serum
A
+
-
B
-
+
AB
+
+
O
-
-
Rh Serum - Clumping = Rh+ blood
A
Rh
B
What is this person’s
blood type?
Answer: A+
Use + or – to show the test results for each sample and then determine the blood type.
Results
+ = Clumping
- = No clumping
Conclusion
What do your results
show?
What would you do next
in the investigation?
Grace Evidence Documentary
7. Where else was high velocity impact
spatter found and what does this indicate?
8. What was wrong with the wound track?
9. What was Scher’s motive?
10. How did Scher change his story when he
saw the forensic evidence?
11. Why was Dr. Scher’s conviction
overturned?
Forensic Science Lab Activity
Warning: Some material in this presentation and
related videos may be too graphic for some people.
T. Trimpe 2006 http://sciencespot.net/
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
Source: http://science.howstuffworks.com/bloodstain-pattern-analysis1.htm
http://www.crimescenetwo.com/img/popup/book2p2.jpg
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.
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 can determine if it is
human blood or not.
Kastle-Meyer Test
Video
Examples:
• Phenolphthalein is a chemical that is still utilized today and is
usually referred to as the Kastle-Meyer test and produces a pink
color when it reacts with hemoglobin.
•HemaStix is a strip that has been coated with
tetramethylbenzidine (TMB) and will produce a green or bluegreen color with the presence of hemoglobin.
HemaStix
Luminol
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.
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).
Luminol
Reaction
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.
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
Types of Bloodstain Patterns
Blood Spatter
Movie
• Passive Bloodstains
– Patterns created from the force of gravity
– Drop, series of drops, flow patterns, blood pools, etc.
• Projected Bloodstains
– Patterns that occur when a force is applied to the
source of the blood
– Includes low, medium, or high impact spatters, castoff, arterial spurting, expiratory blood blown out of
the nose, mouth, or wound.
• 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.
Images from http://www.bloodspatter.com/BPATutorial.htm
Blood Spatters
May Reveal:
•
•
•
•
•
•
•
Origin(s) of bloodstain
Distance of bloodstain from target
Direction from which blood impacted
Speed with which blood left its source
Position of victim & assailant
Movement of victim & assailant
Number of blows, shots, etc.
Liquid Blood
• Behaves as a projectile in motion
– Gravity as only force – falls vertically
– Gravity with another force – falls vertically and
horizontally at the same time
Surface Tension
• Resistant to penetration & separation
• Acts to reduce surface area
• A sphere offers the smallest surface area to
volume ratio so free falling blood drops are
spherical (not “teardrop”) on impact
Dripping Blood
Gravity is the only force acting
Blood drop grows until Wt (G) > S.T.
Single drop breaks free (teardrop shape)
Surface tension pulls in vertically
And horizontally
Shape settles into sphere (0.05 ml volume)
Does not break up until impact
Factors Affecting Drop Size
Rapid bleeding gives
Standard drop
size 50ul (0.05ml) slightly larger drop
Shaking/movement
casts off smaller drops
Breaks surface tension
.
.
.
Shape & Size of Bloodspot
• Depends mostly on nature of target surface
– Texture (rough or smooth)
– Porous or non porous
– Angle of impact
• Size is also related to distance fallen
– Given a standard 50 ul drop of blood
• There is little change in spot diameter
beyond a fall distance of 4 ft (1.2m)
Drop Size vs. Height Fallen
Single drops of blood falling from fingertip onto
smooth cardboard from various heights.
No change in diameter beyond 7 ft.
Adapted from
Introduction to Forensic Sciences,
W. Eckert, CRC, 1997
A blood droplet falling from various heights (ft) onto various surfaces (90 degrees)
1.5
1.5
3
3
Height/Surface
7
7
10
10
smooth
floor
paper
towel
fabric
Angle of
Impact
90
80
70
60
50
40
30
20
Elongated shape; more
dense at lower edge
10
Adapted from
Introduction to Forensic Sciences,
W. Eckert, CRC, 1997
David Sadler:
Wave Cast-off
Angles < 20 degrees to surface
Tail of elongated stain
points in direction of travel
.
Tail of wave cast-off points
back to parent drop
Parent drop
wave cast-off
5 ml of blood squirted from a
syringe from a height of 1m
Point of Convergence
Direction and Origin
• Point of Convergence
– Two dimensional
– Shows direction
• Point of Origin
– Three dimensional
– Shows direction and height
Point of Convergence
Height above point of convergence
Point of Origin
Origin
length
width
Angle of impact = arc sin W/L
(Parent Drop)
85
60
45
Distance from point of convergence
30
Tracing Origin of
Bloodspots
• Point of convergence method
– 2 dimensional; shows direction
• Point of origin method
– 3 dimensional; to include height
• In practice:
– use of string & protractor at scene
– use of computer at laboratory
Blood Spatter Velocity
• Low velocity (5 f/s, 1.5 m/s)
– Free-falling drops, cast off from weapon
• Medium velocity (25 - 100 f/s, 7.5 - 30 m/s)
– Baseball bat blows
• High velocity (>100 f/s, >30 m/s)
– Gunshot, machinery
Low Velocity Blood Spatter
• Blood source subjected to LV impact
– < 5 f/s (1.5 m/s)
• Spot diameter: mostly 4 - 8 mm
– some smaller, some larger
•
•
•
•
•
Free-falling drops (gravity only)
Cast off from fist, weapon, etc.
Dripping (blood droplets into themselves)
Splashing (stepping, throwing, etc.)
Arterial spurting
Cast-off from Weapon
• First blow causes bleeding
• Subsequent blows contaminate weapon with
blood
• Blood is cast-off at a tangent to arc of upswing
or backswing (90 degrees)
• Pattern & intensity depends on:
– type of weapon
– amount of blood adhering to weapon
– length of arc, swing
Downswing of Hammer
Dripping Pattern
•
•
•
•
Free-falling drops dripping into wet blood
Falling from a stationary object
Large irregular central stain
Small round & oval satellite stains
.
.. ..
. .
.
.
.
. ..
. .. . .
Blood dripping into itself from height of 1 m (8 drops)
Notice Irregular Central Stain
Drip 1:
Blood dripping into itself from height of 1 m (8 drops)
Closer View Showing Round and Oval Satellite Stains
Drip 2
Splash Pattern
• Volume > 1 ml
– Subjected to LV impact
– Thrown
– Tipped
• Large central irregular area surrounded
by elongated peripheral spatter pattern
Splash 1
5 ml blood squirted from a syringe from a height of 1m
5 ml blood squirted from a syringe from a
height of 1 m (Closer View of Central Stain)
Splash 2
5 ml blood squirted from a syringe from a height of 1 m
(Closer View of Peripheral Stains) Direction?
Splash 3
Splashing on a vertical
surface
10 ml blood thrown 1 m
onto a vertical surface
6” ruler
Blood pool (10 drops) before stamping
Stamp 1
Blood pool (10 drops) after stamping with shoe
Stamp 2
Arterial Spurt Pattern
• Blood exiting body under arterial pressure (120 mm
Hg); corresponds to heart beating
• Large stains with downward flow on vertical
surfaces; air bubbles present if lung was punctured
• Creates a wave-like appearance
Arterial Spurt Pattern
Medium Velocity
Blood Spatter
• Blood source subjected to MV impact
– (25 - 100 f/s, 7.5 - 30 m/s)
• Spot diameter: mostly 1 - 4 mm
• Blows with weapon (baseball bat, etc)
Cast-off (LV) & Medium Velocity Spatter
Cast-off & Medium Velocity Spatter (Close-up)
High Velocity Blood Spatter
• Blood source subjected to HV impact
– > 100 f/s, 30 m/s
•
•
•
•
Fine mist: spot size < 0.1 mm
Small mass limits spread to 1 m
Some larger droplets reach further
Gunshot
– back-spatter from entry wound
– forward spatter from exit wound
• High speed machinery
Gunshot: Back & Forward Spatter
Bloodstained foam held just above target surface.
Bullet passing L to R just above sheet
bullet exits foam
Bullet enters
foam
bullet
Back spatter
on entry
Forward spatter
on exit
Gunshot Back Spatter
•
•
•
•
Arises from entrance wound
Passes back towards weapon & shooter
Seen only at close range of fire
Seen on:
– inside of barrel
– exterior of weapon
– hand, arm, chest of shooter
Back spatter
on
steadying
hand
Gunshot Forward Spatter
•
•
•
•
•
Arises from exit wound
Passes forward in same direction as shot
More copious than back-spatter
Can be seen at any range of fire
Seen on nearby surfaces, objects, persons
– especially on wall behind victim
Forward spatter (5 ms after bullet impacted at 1000 f/s)
bullet
blood soaked
target
Forward spatter on a target (15cm from exit point) due
to a HV impact (bullet)
6” ruler
Forward Spatter (closer view to show misting)
Forward Spatter (closest view) Droplet Size 0.1mm
5 mm
Other Patterns
• Bloodstain patterns that have been altered
– Altered by objects, gravity, others
• Include:
–
–
–
–
Wipe Patterns
Swipe Patterns
Transfer Patterns
Flow Patterns
Wipe and Swipe Patterns
• Wipe
– Object moves through a wet bloodstain
– Removes and/or alters bloodstain appearance
– Does not require a swipe pattern be present
• Swipe
– Transfer of blood to an unstained surface
– Direction may be determined by feathered edge
– A wipe pattern must also be present
Transfer Patterns
• Wet, bloodied object contacts a secondary
surface
• Transfer from:
– hand, fingers
– shoes, weapon
– hair
• Transfer to:
– walls, ceilings
– clothing, bedding
• Produces mirror-image of bloodied object
Transfer from hair
Flow Patterns
• Blood flows horizontally & vertically
• Altered by contours, obstacles
• Often ends in pool
Flow Pattern Showing Pooling of Blood
Homework
Chapter 8 Review, #1-25 due Monday
Forensic Files Friday