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Blood Spatter Analysis
Transcript of Blood Spatter Analysis
Analysis IS IT BLOOD? WHAT IS BLOOD? Noun:
The red liquid that circulates in the arteries and veins of vertebrate animals, carrying oxygen to and carbon dioxide from the tissues...
An internal bodily fluid, not necessarily red, that performs a similar function in invertebrates. blood: Components of Blood Solid Portion of Blood
Red Blood Cells
White Blood Cells
45% of blood Liquid Portion of Blood
55% of blood RBC contain hemoglobin, which is ONLY found in blood, therefore, is useful in the identification Components of a RBC RBC's transport oxygen from the lungs to the body and remove carbon dioxide from tissues and transport it back to the lungs. The molecule responsible for this transport is Hemoglobin. The surface of a RBC contains antigens
Antigen (Ag) – a glycoprotein that stimulates the body to produce antibodies (Ab) against it
Antigens impart blood-type characteristics to the RBC Antigens & Antibodies Rh factor or D antigen – people having the D antigen are Rh positive; those without are Rh negative
Antibodies (Ab) are proteins found in the serum that destroy or inactivate a specific Antigen (Ag)
The fundamental principle of blood typing is that for every antigen, there exists a specific antibody. An Ab will react only with its specific antigen
Ab are normally bivalent – having 2 reactive sites
Each Ab can simultaneously be attached to antigens on 2 different RBC
This creates a network of cross-linked cells seen as clumping or agglutination Blood Typing Blood typing was used as an important diagnostic tool for forensic investigators until the early 1990's. It could help determine the type of blood and eliminate suspect from our pool based on blood type. It also gave strong evidence to link the suspect to the scene.
What are the problems with ABO/Rh blood typing?
What technology replaced blood typing? Identification of Blood A Forensic Investigator must answer the following questions when examining dried blood or any blood for that matter:
1.) Is it blood?
2.) From what species did it originate?
3.) If the blood is human, can it be individualized. (Who's blood is it?) Two general types of test for Blood:
Color Change, Luminescence, & Fluorescence
Doesn't tell us species of origin
Microcrystalline & Precipitin
Gives us species of origin Presumpitve Tests Color Tests Chemiluminescence Fluorescence Benzidine Color Test For many years the Benzidine color test was a standard as a presumptive test for blood. It was found to be a carcinogenic and it's use has been discontinued. Kastle-Meyer Test Phenolphthalein has been substituted for Benzidine.
Blood is picked up with typically a q-tip
Phenolphthalein and hydrogen peroxide are added
The mix of the blood, Phenolphthalein, and peroxide will yield a deep pink color
It is not specific for blood, and can have false positives (potatoes and horseradish) Color tests such as the Benzidine and Phenolphthalein test are a result of peroxidase like activity that is expressed by hemoglobin. Peroxidases are a class of enzyme that accelerate the oxidation of organic material when combined with peroxide. Hemastix Field investigators have found the use of hemastix very useful
Originally designed to detect blood in urine
strip is moistened with distilled water and placed in contact with the stain
a green color indicates blood
Up to 1992 o-tolidine was the active ingredient in Hemastix, it was derivative of Benzidine (Carcinogenic!)
Post 1992 Diisopropylbenzene Dihydroperoxide, Tetramethylbenzidine Is the process by which light is emitted as a PRODUCT of a chemical reaction. No additional light is required for the reaction to take place. Spray area
View in complete darkness
Bloodstains will luminesce within 5 sec
Best on area where there has been an attempt to clean up; capable of detecting blood dilute up to 100,000 times
Won’t interfere with subsequent DNA testing
Because of its transient nature, photograph for records Luminol Bluestar Luminol based
Uses different reagents for visualization
Does not need total darkness
It is more sensitive than luminol
Occurs when a chemical substance is exposed to a particular wavelength of light (usually a short wavelength, such as UV) and light energy is emitted at longer wavelengths. Requires alternate light source to see. Purpose is to define/enhance patterns not visible but thought to be present
Cover VISIBLE blood first to avoid chemical contamination
Contains a commercial thickener that causes the mixture to adhere to the surface – good on vertical areas
Requires alternate light source to view fluorescence
Does not destroy DNA evidence Fluorescein Confirmatory Tests Microcrystalline Tests Precipitin Test Confirmatory tests are not as sensitive as the screening tests, but are necessary to prove that the stain is, in fact, blood
Microcrystal tests – chemical reagents react with heme components of the blood and produce characteristic crystals Teichmann Crystals Takayama Crystals Precipitin Tests are based on the fact that when animals are injected with human blood, antibodies are formed that react with the invading human blood; the Antibodies are recovered and used to specifically react with human antigens = human blood Precipitin tests are very sensitive and require small amounts of blood
Human stains dried for as along as 10-15 years may still give a positive result
Even extracts of tissue from mummies have given positive reactions! http://www.bluestar-forensic.com/gb/hexagon.php Collection of Blood
Collection and packaging MUST be done properly or all test results will be irrelevant Collection of Blood Evidence Fresh, liquid blood – use syringe or pipette and place into EDTA vial (EDTA keeps blood from clotting)
Fresh, wet, thick, clotting – add equal volume saline to preserve RBC
Whole blood from a living person – collect in EDTA vial and transport immediately
Crusts of dried blood – scrape into vial, paper, fold then envelope, or lift with tape Stained knives, rocks – submit the item
Upholstery, rugs, fabric – cut out section and submit
Walls – moisten q-tip with saline and swab area, air dry, or tape lift
Large stains – scrape the stain into paper, fold then place in envelope
Clothing – air dry, keep out of direct sunlight, put each item in separate bag, may wrap in paper Types of Items and Areas blood may be collected from: http://www.bd.com/vacutainer/pdfs/techtalk/TechTalk_Jan2009_VS8014.pdf Packaging of Blood Evidence Always transport body fluids in paper.
Plastic provides an anaerobic environment which encourages the growth of bacteria. Bacteria can break down the proteins and destroy the hemoglobin.
Each bloody item should be packaged separately to prevent cross contamination Consider all blood and body fluids infectious, whether wet or dry
Handle all needles, syringes, blades, and knives with caution; place in puncture-resistant containers
Wash hands with soap and water after each assignment or when contaminated
Keep all wounds carefully bandaged Collection Precautions Wear gloves when handling objects that may be contaminated by bodily fluids
Wear gowns and eye protection when your clothing may be soiled by blood or body fluids, or when performing procedures which may involve exposure to potentially infectious body fluids
Avoid hand to face contact, eating, & drinking
Clean up contaminated surfaces and objects with a solution of 1 part bleach to 9 parts water
Constantly be alert of sharp objects! Blood Spatter Analysis General Guidelines Violent crimes many times involve bleeding and bloodstain patterns. This can be deposited on walls, floors, ceilings, bedding, furniture, and other relevant objects. Information from Bloodstains patterns:
The direction the blood originated
The angle at which the blood droplet struck the surface
The location or position of the victim
The movement of a bleeding individual
The minimum number of blows to a victim
Approximate location of the suspect while striking the victim http://www.pbs.org/wgbh/nova/sheppard/ http://www.trutv.com/library/crime/notorious_murders/famous/sheppard/index_1.html Sam Sheppard Case Lizzie Borden Case http://www.trutv.com/library/crime/notorious_murders/famous/borden/index_1.html Blood Droplets Surface texture is paramount in the interpretation of blood stain patterns.
Smooth surfaces leave a bloodstain with less satellite spatter
Glass, smooth tile, etc..
Rough surfaces leave a bloodstain will satellite spatter
carpeting, wood, etc....
Comparisons must be made on similar surfaces
Height from which blood is deposited from will also impact the size of the droplet
The speed at which the blood is deposited will do the same thing.
The angle at which blood is deposited will elongate the droplet from a circle to an elipse. Directionality & Angle The geometry of individual stains will generally provide info as to the direction of flight prior to impacting an object
The narrow end of an elongated bloodstain usually points in the DIRECTION of TRAVEL Area of Convergence Draw straight lines through the long axis’ of the blood spots
Where these lines converge represents the area of convergence (area not pinpoint) Area of Origin It may be important to an investigation to determine the three dimensional space from which the blood was projected. This is known as the AOO.
This can show the position of the victim or suspect in the space
The angle of impact needs to be calculated first. Calculation:
Measure width and length of drop
Divide width by length (gives a number ‹1.0)
Take the sin-1 of that number for the angle of impact To calculate the AOO:
Find the area of convergence for the satin pattern
Place a pole or a stand as an axis coming from the area of convergence
Attach one end of a string next to each droplet. Place a protractor next to each droplet and lift the string until it lines up with the determined angle of impact of the drop. Keeping the string in line with the angle, attach the other end of the string to the axis pole
View the AOO of the drops where the strings appear to meet. Secure the strings to this area Types of Blood Stain Patterns General Types of Patterns Low Velocity Spatter Blood droplets will be 3mm or more in diameter
blood droplet was moving at rate less than 1.5m/sec
Typically blood falling from wounds Medium Velocity Spatter Blood droplets are 1-3mm in diameter
Blood droplet was moving at a rate from 1.5-7m/sec
Typically indicates blunt force trauma High Velocity Spatter Blood droplets are smaller than 1mm in diameter
Blood droplet was moving at a rate greater than 30m/sec
Typically indicates gunshot wounds or wounds from high speed machinery Specific Types of Patterns Gun Shot Spatter High Velocity
Cone shaped pattern
Larger cone on the exit wound
Smaller cone on the entry wound (blow back spatter) Cast-off Blood Spatter Medium Velocity spatter
Typically caused by blunt force
Fist / Weapon
Width of the pattern can suggest the type of weapon
Size of the drops are directly related to the size of the object used What can we learn from cast-off spatter? Smaller the stain = less volume of blood
Pattern may suggest handiness of the suspect.
Are the blows from R to L or L to R
The pattern will point to the direction of backward thrust
Can also indicate the number of blows Arterial Spray / Expirated Blood Pattern Arterial Spray Victim sustains an injury to a major artery
Pressure from the pumping heart, propels blood out of the wound and causes it to spurt
There should be stain pattern for each time the heart beats
The line-up of stains will show the direction of travel of the victim Expirated Blood Stain Patterns Blood that is expelled from the mouth and nose
Can be both high velocity & low velocity spatter
Under pressure like a cough or a sneeze = high velocity
Under low pressure = breathing
Stain cluster with an irregular edge
May have air bubbles
May be lighter in color due to the influence of saliva
Saliva changes the physical characteristics of blood Void Patterns When an object blocks the deposition of blood
Once the object in question is found, the missing pattern should be on the object, or the object should fit in void Alternate Bloodstain patterns Contact / Transfer Patterns -When an object with blood on it touches another one that does not have blood on it. This will produce the contact pattern.
-ex. fingerprints, handprints, footprints, footwear prints, tool prints, and fabric prints in blood. Flows and Pools -Flow Patterns- made by drops or large amounts of blood flowing by the pull of gravity. Can come from an actively bleeding wound or arterial spray deposited on a surface. -Pools- occurs when blood collects on a level undisturbed surface Drip Trail Patterns -A series of drops that are separate from other patterns, and are typically formed by blood dripping off an object or injury.
-Stain will typically for a line or path made by the suspect or victim.