Warm-UpNovember 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. Blood Typing Lab

2. Grave Evidence Documentary

3. Bloodstain Patterns

4. Blood Spatter Lab

5. Forensic Files Friday

Forensic Science

Blood Typing Lab Activity

T. Trimpe 2006 http://sciencespot.net/

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

The Crime Report

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 -).

Clumping = + (Positive) No Clumping = - (Negative)

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.

Blood Typing Test

Rh Serum - Clumping = Rh+ blood

TypeReaction w/

Anti-A SerumReaction w/

Anti-B Serum

A + -

B - +

AB + +

O - -

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.

Agglutination = Clumping = Positive Reaction

Clumping = Positive Result

A

B

Rh

What is this person’s blood type?

Answer: A+

Rh Serum - Clumping = Rh+ blood

TypeReaction w/

Anti-A SerumReaction w/

Anti-B Serum

A + -

B - +

AB + +

O - -

What do your results show?

What would you do next in the investigation?

Conclusion

- = No clumping

+ = Clumping

Results

Use + or – to show the test results for each sample and then determine the blood type.

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

T. Trimpe 2006 http://sciencespot.net/

Warning: Some material in this presentation and related videos may be too graphic for some people.

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

http://www.crimescenetwo.com/img/popup/book2p2.jpg

How does a blood droplet

form? Click the image

for an animation.

Source: http://science.howstuffworks.com/bloodstain-pattern-analysis1.htm

Light SourceInvestigators 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 TestsThese 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.

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 blue-green color with the presence of hemoglobin.

Kastle-Meyer TestVideo

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. Luminol

Reaction

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.

FluoresceinThis 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

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

Spines

Satellite Spatters• 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.

• 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, cast-

off, 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 Spatter Movie

Types of Bloodstain Patterns

Blood SpattersMay 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

Blood drop grows until Wt (G) > S.T.

Single drop breaks free (teardrop shape)

Surface tension pulls in vertically

Shape settles into sphere (0.05 ml volume)

Does not break up until impact

And horizontally

Gravity is the only force acting

Factors Affecting Drop Size

.

Standard drop size 50ul (0.05ml)

.

Rapid bleeding gives slightly larger drop

Shaking/movementcasts off smaller dropsBreaks 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

Height/Surface

A blood droplet falling from various heights (ft) onto various surfaces (90 degrees)

smooth floor paper towel fabric

1.5

3

7

10

1.5

3

7

10

Angle of Impact

90

10

70

2030

60 50 40

Adapted from Introduction to Forensic Sciences,W. Eckert, CRC, 1997

80

Elongated shape; more dense at lower edge

Wave Cast-offAngles < 20 degrees to surface

David Sadler:David Sadler:

.Parent drop

wave cast-off

Tail of wave cast-off points back to parent drop

Tail of elongated stain points in direction of travel

Point of ConvergencePoint of Convergence5 ml of blood squirted from a syringe from a height of 1m

Direction and Origin

• Point of Convergence– Two dimensional– Shows direction

• Point of Origin– Three dimensional– Shows direction and height

Point of Convergence

Point of Origin

length

width

Angle of impact = arc sin W/L

(Parent Drop)

Distance from point of convergence

Hei

ght a

bove

poi

nt o

f co

nver

genc

e

Origin

85 60 45 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

.. .......

Drip 1:Drip 1:

Blood dripping into itself from height of 1 m (8 drops)Notice Irregular Central Stain

Drip 2Drip 2

Blood dripping into itself from height of 1 m (8 drops)Closer View Showing Round and Oval Satellite Stains

Splash Pattern

• Volume > 1 ml – Subjected to LV impact – Thrown – Tipped

• Large central irregular area surrounded by elongated peripheral spatter pattern

Splash 1Splash 1

5 ml blood squirted from a syringe from a height of 1m

Splash 2Splash 2

5 ml blood squirted from a syringe from a height of 1 m (Closer View of Central Stain)

Splash 3Splash 3

5 ml blood squirted from a syringe from a height of 1 m (Closer View of Peripheral Stains) Direction?

Splashing on a vertical surface

6” ruler

10 ml blood thrown 1 m onto a vertical surface

Stamp 1Stamp 1

Blood pool (10 drops) before stamping

Stamp 2Stamp 2

Blood pool (10 drops) after stamping with shoe

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.

Back spatter on entry

Forward spatteron exit

bullet

Bullet passing L to R just above sheet

Bullet enters foam

bullet exits foam

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)

2.5 cm

blood soaked target

bullet

6” ruler

Forward spatter on a target (15cm from exit point) due to a HV impact (bullet)

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