Presumptive Tests for Blood DeterminationIs it blood?

Leucomalachite test - a mixture of leucomalachite green, acetic acid and distilled water is placed on sample; then a drop of sodium perborate added will turn blood a green-ish colour.

Question to be answered: Is it blood?

Light SourceUse a high-intensity light or UV lights

Kastle-Meyer test a mixture of phenolphthalein and hydrogen peroxide; the hemoglobin will cause the formation of a deep pink colour if blood is present.

• HemaStix is a strip that has been coated with tetramethylbenzidine (TMB) and will produce a green or blue-green colour with the presence of hemoglobin.

Kastle-Meyer TestVideo

HemaStix

Is It blood?

Luminol

Luminol Reaction

Presumptive Tests for Blood DeterminationIs it blood?

LCV or Leuco Crystal Violet

FluoresceinIt is also capable of detecting latent or old blood, similar to luminol. It may also react to many of the same things as luminol (copper and bleach).

Fluorescein Reaction in

UV Light

Presumptive Tests for Blood Determination

Unknown stain at the scene

Question to be answered: Is it human blood?

Unknown stain at the scene

Human blood vs Animal blood Microscopic observation

Precipitin test - human blood is injected into a rabbit; • Human antibodies are

formed; • the rabbit’s blood is

extracted as an antiserum; • the antiserum is placed on

sample blood.

Larger nucleic red blood cells

Frog Blood

Animal Blood

• The sample will react with human proteins, if human blood is present.

• This test is very sensitive and requires only a small amount of blood.

Microscopic Views

Bird Blood

Cat Blood

Dog Blood

Fish Blood

Frog Blood

Snake BloodHuman Blood

Horse Blood

Components of blood

7

Antigen determines blood type

Antibody

ABO Blood Types

Rhesus Blood Types

Other proteins can distinguish blood (Rh, MN, etc.) 85% of Caucasians, 94% of Black Americans and 99%

of all Asians are Rh positive. Antigen-Antivody reactions determine blood types

http://www.bloodservices.ca/centreapps/internet/uw_v502_mainengine.nsf/page/Percentage-of-Blood-Types-In-Canada?OpenDocument

• The distance between the target surface and the origin of blood

• 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 does a blood droplet

form? Click the image

for an animation.

Questions Answered by Bloodstain Pattern Analysis

Blood splatter

Blood Droplet Characteristics A droplet contains

approximately 0.05 cc of fluid

Is not the same for all blood droplets, but is generally from 0.03 cc to 0.15 cc

Blood Droplet Volume

Is directly dependent upon the surface or orifice from which it originates

The impact area is called the target.

Blood evidence

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.

Parent Drop

Spines

Satellite SpattersParent Drop –

Satellite Spatters –

Spikes or Spines –

Bloodstain Terminology

Blood evidence

Wipe - a non-blood bearing object moves through a wet bloodstain, altering the appearance of the original stain

Directionality—relates to the direction a drop of blood traveled in space from its point of origin

Terminal velocity - the greatest speed to which a free falling drop of blood can accelerate in air. It is dependent upon the acceleration of gravity and the friction of the air against the blood—approximately 25.1 feet/second.

Medium velocity

Low velocity

High velocity

Bloodstain Terminology

Blood evidence

Bloodstain TerminologyAngle 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 surface

Backspatter—Cast-off—blood that is thrown from an object in motionContact stain - bloodstains caused by contact between a wet blood-bearing surface and a second surface which may or may not have blood on it

Transfer - an image is recognizable and may be identifiable with a particular objectSwipe - wet blood is transferred to a surface which did not have blood on it

Conditions Affecting Shape of Blood Droplet

Blood evidence

Passive Bloodstains

Projected Bloodstains

Transfer or Contact Bloodstains

General Types of Bloodstain PatternsBlood splatter analysis

Describe each of these based on the images above:

Blood splatter analysis

There are six patterns that blood can form.

1) Passive drops 3) Arterial gushes2) Splashes

4) Smears 5) Trails 6) Pools

Blood splatter analysisPassive Drops

Stage 1: contact & collapse Stage 2: displacement

Stage 3: dispersionStage 4: retraction

Stages of Impact

. .... .Spreads out smoothly

ST of spreading edge is broken by irregular surface

The harder and less porous the surface, the less the blood drop will break apart.

The softer and more porous the surface, the more a blood drop will break apart.

Blood splatter analysisPassive Drops

Effect of Target Surface

.... ...

..

..

Free-falling drops dripping into wet bloodLarge irregular central stainSmall round & oval satellite stains

Drip Pattern

Blood splatter analysisPassive Drops

Wave Cast-off

.Parent drop

wave cast-off

Tail of wave cast-off points back to parent drop

Tail of elongated stain points in direction of travel

Impact at An Angle

Point of Origin

length

width

Angle of impact = arc sin W/L

Distance from point of convergence

Heig

ht

ab

ove p

oin

t of

con

verg

en

ce

Origin

85 60 45 30

Blood splatter analysisImpact Angle

Point of Convergence and Origin

The Point of Convergence:

The Point of Origin

Blood splatter analysisImpact Angle Point of Convergence

Point of Origin

Tracing Origin of Bloodspots Point of convergence method• 2 dimensional image

Point of origin method• adds 3rd dimension to

image In practice:

• use of string & protractor at scene

• use of computer at laboratory

Low velocity (5 f/s, 1.5 m/s) Medium velocity (25 - 100 f/s, 7.5 - 30

m/s) High velocity (>100 f/s, 30 m/s)

Blood splatter analysisImpact Angle

Large central irregular area surrounded by elongated peripheral spatter pattern

Blood splatter analysisSplashes

Patterns can help investigators determine the type of weapon used.

• What kind of a pattern is produced by a gun shot? • What kind of a pattern is produced by a hammer blow?

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

Blood splatter analysisSplashes

6” ruler

Point of impact 15 cm in front of vertical target surface

ceiling

Medium Impact Medium impact occurs when a force such as a bat is applied. The pointed end of the blood stain faces the direction of travel.

Cast-off from Weapon Blood is cast-off

tangentially to arc of upswing or backswing

Pattern & intensity depends on:• type of weapon• amount of blood

adhering to weapon• length of arc

Arterial Gushes Medium velocity Blood exiting body under arterial pressure Large stains with downward flow on vertical surfaces Wave-form of pulsatile flow may be apparent

Blood splatter analysis

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

High Velocity SplatterBlood splatter analysis

High impact - fine mist of droplets

Gunshot: back & forward spatterBlood stained 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

High Velocity SplatterBlood splatter analysis

Flow Patterns Blood flows horizontally & vertically Altered by contours, obstacles Often ends in pool

Trails and Pools

Blood splatter analysis

400X

Other aspects of serologySemen

Males release 2.5 to 6 milliliters of seminal fluid per ejaculation with approximately 100 million sperm per milliliter

Determination of Seminal Fluid Acid phosphatase colour test

• The presence of acid phosphatase, the enzyme secreted by the prostate gland into the seminal fluid, will turn purple when sodium alpha naphthylphosphate and Fast Blue B solution are placed on it.

Sperm

• It will also fluoresce under UV light when it comes in contact with 4-methyl umbelliferyl phosphate.

Determination of Seminal Fluid Prostate Specific Antigen (PSA) or p30 – unique to seminal plasma

• P30 is isolated and injected into a rabbit where antibodies are produced (anti-p30).

• The stain extract is place in one well of an electrophoresis plate and the anti-p30 in the opposite well. The electric is applied and the antigens and antibodies move toward each other. The formation of a precipitation line between the wells shows the presence of p30 in the sample stain. It, therefore, must be seminal fluid.

Secretors

80% of the population are secretors. Their blood-type antigens are found in high concentration in their body fluids such as saliva, semen, vaginal secretions and gastric juice.

Your Task:Your group will create a bloody

crime scene for another group to analyze.

HW: Write the scenario you will create and how you will create it. Write down how you will analyze the unknown blood spatter from the other group.

Bring: Garbage bag/old clothes, goggles, protractor, tools and object to hit (wooden block), calculator