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Transcript of Leucomalachite test - a mixture of leucomalachite green, acetic acid and distilled water is placed...
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
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