Students will investigate the characteristics of blood, blood testing, and bloodstain analysis. Unit 6 serology. Erythrocytes Leukocytes Thrombocytes Plasma Antigen RBC WBC Rh Factor Bloodstain Pattern Analysis Surface Tension Low-velocity impact splatter (LVIS)
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Bloodstain Pattern Analysis
Low-velocity impact splatter (LVIS)
Medium-velocity impact splatter (MVIS)
High-velocity impact splatter (HVIS)
Cast off pattern
Solid portion of the blood
1. Red blood cells (RBC).
2. Contain hemoglobin that transports the oxygen and carbon dioxide.
3. Concave in structure.
4. Approximately 30 trillion in the blood.IDENTIFY THE Components AND PHYSICAL PROPERTIES OF BLOOD
1. White blood cells (WBC).
2. Provide immunity for the body and produce antibodies.
3. There are 5 types of white blood cells.
4. Approximately 430 billion in the blood.IDENTIFY THE COMPONETS AND PHYSICAL PROPERTIES OF BLOOD
1. Platelets (pieces of larger cells).
2. Responsible of starting the clotting process by making fibrin to form a clot.IDENTIFY THE COMPONETS AND PHYSICAL PROPERTIES OF BLOOD
1. Fluid portion of the blood that carries the RBC, WBC, and platelets.
2. 55% of blood is the plasma.
3. Made up of 90% water and 10% metabolites (salt, ions, and proteins).IDENTIFY THE COMPONETS AND PHYSICAL PROPERTIES OF BLOOD
1. Proteins found on the surface of every RBC.
2. There are over 100 different antigens in the human blood.
3. Two of the antigens, labeled as A and B, are the ones used on the RBC surface to determine blood type.ANTIGENS AND ANTIBODIES THAT DETERMINE ABO BLOOD TYPES AND THE Rh FACTOR
Punnet Squares: A parent passes on one of two genes for blood type to the offspring. One of two genes is also passed on for the Rh factor. In order to be recessive in type or Rh, BOTH genes must be recessive. Using a Punnet square can determine if a blood type is possible in an offspring. This is useful in many ways, one of the most common being paternity.Determine genetic probabilities using blood types
If a child’s blood type is AB+, the mother’s type is AB+ and the father’s type is O-, could the “father” be the genetic father?Determine genetic probabilities using blood types
5 to 6 liters of blood for males
4 to 5 liters of blood for females
A 40 percent blood volume loss, internally or/and externally, is required to produce irreversible shock (death).
A blood loss of 1.5 liters, internally or externally, is required to cause incapacitation.Properties of blood
80% of the population are secretors.
A secretor is a person who has the gene to secrete blood type substances (A, B & H)in a soluble glycoprotein form in their body fluids, like saliva, tears, gastric juice, etc.
The “A” and “B” substances are derived from the “H” substanceBlood Typing Using Saliva
If the cells clump (agglutination), the person is a non-secretor
Lectin is a plant substance that reacts with blood group substances
The lectin will indicate if an H substance is present in the blood (an H substance is the A or B)Blood Typing Using saliva
If H group is present, then anit-A serum and anti-B serum can be added to determine blood groupBlood typing using saliva
Before blood can be used as evidence, it must first be confirmed to be blood.
Test 1: Presumptive Blood test. This test shows the presence of hemoglobin. It is not human specific.
“Every contact leaves a trace.”
Blood evidence is extremely important in forensics. It can be used to determine the nature of the crime, blood types, DNA, recreate a crime scene, etc.Blood detection labs
However, running blood tests and DNA tests is very time consuming and expensive. If a sample is sent to a lab for processing, it is best to know if the sample is most likely blood or not.
A presumptive blood test “presumes” a substance is blood if it reacts to chemicals in a particular way.
The most common presumptive test that is run is the Kastle-Meyer Test .Presumptive blood Test
Kastle-Meyer is quick, inexpensive, easy and does not compromise the integrity of the sample, like DNA. It is very sensitive, 1:10,000. One drop of blood diluted 10,000 times with water can still be detected.
It does not distinguish between human and animal blood. It detects the iron in hemoglobin, so other products with iron could also give a positive result.Kastle-meyer test
Products used: Alcohol (cleans sample and exposes more hemoglobin), phenolphthalein (changes color with oxidation – tells you if the test is bad and you need to redo it), hydrogen peroxide (releases extra oxygen, causes the pink color if oxygen is released from the hemoglobin)
Test 2: Luminol Test. This test shows where blood has been present but wiped away. It can also react to a number of substances such as copper or copper-containing alloys, and certain bleaches; and, as a result, if a crime scene is thoroughly cleaned with a bleach solution or horseradish, residual cleaner will cause the entire crime scene to produce the typical blue glow, effectively camouflaging any organic evidence, such as blood. Luminol reacts with fecal matter, causing the same glow as if it were blood.Blood detection labs
Surface TensionThe elastic like property of the surface of the liquid that makes it tend to contract,caused by the forces of attraction between the molecules of the liquid.The cohesive forces tend to resist penetration and separation.
Bloodstain Pattern Analysis:is the examination of the shapes, locations, and distribution patterns of bloodstains, in order to provide an interpretation of the physical events which gave rise to their origin.
Based on the premise that all bloodstains and bloodstain patternsare characteristic of the forces that have created them.blood spatter
The determinations made from bloodstain patterns at the scene or from the clothingof principals in a case can be used to:
Confirm or refute assumptions concerning events and their sequence:Position of victim. (standing, sitting, lying)Evidence of a struggle. (blood smears, blood trails) n
Confirm or refute statements made by principals in the case:Are stain patterns on a suspects clothing consistent with his reported actions?Are stain patterns on a victim or at a scene consistent with accounts given by witnesses or the suspect?
At a crime scene the blood spatter patterns are photographed before the blood is collected so that the suspects account can be proved or disproven. The photographs will allow for an interpretation and reconstruction of what happened.
1. Recorded with micro scales visible in photographs.
2. Shape of the mark where it lands reveals the direction in which the drop was traveling and the amount of force it was projected with.
C. Directionality of blood spatter
1. The pattern that indicated the direction the blood was traveling when it hit the target surface.
2. Established from the geometric shape of the bloodstain.Blood Spatter
Passive Bloodstains are drops created or formed by the force of gravity acting alone.
Drops, drip patterns, pools, clots
Drip pattern: A blood stain pattern that results from blood dripping into blood.Blood Spatter Patterns: Passive
A transfer bloodstain is created when a wet, bloody surface comes in contact with a secondary surface.
Swipe or smear
smudgeBlood Spatter Patterns: Transfer
Projected bloodstains are created when an exposed blood source is subjected to an action or force, greater than the force of gravity. (Internally or Externally produced)
ExpiratedBlood Stain Patterns: Projected
A. Drip pattern: A blood stain pattern that results from blood dripping into blood.
IN the Forensics book, pages 231-232, there are 35 blood spatter terms. Create flashcards for each term.
For the terms which describe how blood spatter looks, create a picture image of what it looks like using water color paints- so your flashcards for the following terms will have a word, a definition and a painted picture exampleBlood Spatter Vocab Cards
The following terms need to have a painted picture: arterial spurting, bloodstain, cast-off pattern, contact stain, drip pattern, expirated blood, flow pattern, HVIS, impact pattern, LVIS, MVIS, misting, parent drop, passive drip, satellite spatter, spatter, spine, swipe pattern, transfer pattern, void, wipe pattern.
For HVIS, MVIS, LVIS, simple put a “drop” mark with the brush that is the right size in diameter.Blood spatter vocab cards
When a droplet of blood strikes a surface perpendicular (90 degrees) the resulting bloodstain will be circular.That being the length and width of the stain will be equal.
Blood that strikes a surface at an angle less than 90 degrees will be elongated or have a tear drop shape.Directionality is usually obvious as the pointed end of the bloodstain ( tail ) will alwayspoint in the direction of travel.Directionality of blood spatter
ANGLE of IMPACTis the acute angle formed between the direction of the blood dropand the plane of the surface it strikesiMpact Angle Determination
By utilizing trigonometric functions its possible to determine the impact angle for any given blood droplet.
SIN 0 = opp (a)
Length (c) 3.0cm
Width (a) 1.5cm = SIN <
Length (c) 3.0cm
0.5 = SIN <
< = 30 degrees
The common point, on a 2 dimensional surface, over which the directionalityof several bloodstains can be retraced.
Once the directionality of a group of stains has been determined,it's possible to determine a two dimensional point or area for the group of stains.POINT OF CONVERGENCE AND ORIGIN DETERMINATION
A. Luminol- Used if a high-intensity light beam does not reveal blood at a crime scene after it has been cleaned.
Semen and saliva are other body fluids which are commonly found at crime scenes.
We will be examining semen from a bull. First, examine the live sperm in the microscope. Draw and describe what you see. How would a sperm count be made? How could a sperm count play a role in being evidence? (class or individual)
Using black light, examine the fabric to see if body fluid is present (in this case, bull semen). Describe the methods you used. Describe what you see.
How would this evidence be collected and sent back to the lab?Semen
This simulated crime scene will require you to use your knowledge of hair, fiber, trace and blood evidence to solve.The Case of loismcarthur