evidence “blood stains” “stomach contents” “hair sample” cut gas line test (human or...
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EvidenceEvidence
““blood stains”blood stains”
““Stomach contents”Stomach contents”
““Hair sample”Hair sample”
Cut gas lineCut gas line
Test (Human or not)Test (Human or not)
DNADNA
Blood TypeBlood Type
HairHair
Further: DNA TestFurther: DNA Test
What is in it?What is in it?
• LiverLiver
• SodaSoda
Who’s blood is it?
Forensic Characterization of Bloodstains
Three questions to answer:
1. Is it blood?
2. From what species did the blood originate?
3. If the blood is human, how closely can it be associated with a particular individual?
How can a
Blood Samplebe used for
identification?
1. IS IT BLOOD?
Presumptive Tests
suggests but does not confirm the presence of blood; indicates that other tests should be performed
• negative result means the substance IS NOT blood
• positive result means the substance IS LIKELY blood (could be)
https://ecrimescenechemistrymiller.wikispaces.com/notes+on+serology
Kastle-Meyer Test (phenolphthalein/peroxidase test)
when a blood stain, hydrogen peroxide and phenolphthalein reagent are mixed,
the oxidation of the hemoglobin in the blood produces a deep pink color
Sensitivity: 1:10,000
(if 1 drop of blood were present in a bucket with 10,000 drops of water, the PHTH test would still turn pink)
hemoglobin - Blood contains hemoglobin (carries oxygen and makes blood red) which contains a heme group which contains an Fe which can catalyze the breakdown of hydrogen peroxide
Spencer Rhodes Black Blond Red
hair hair hair
Student
Stephen Sasz Evan Roberts David Host
Who’s blood is it?
Red Blood Cell
The cell membrane of RBCs has molecules in its surface that act as identification badges so immune system can recognize it as a normal component.
Normal Foreign
CHEMICAL MARKERS
IMMUNE SYSTEM
ANTIBODIES
BLOOD TYPES
Blood can be classified by either:
A. Blood Type ABO
identified by the type of antigen
(antigen A or antigen B)
B. Rhesus Factor
another type of antigen
(Rhesus positive or Rhesus negative)
So, what is an ANTIGEN?
The differences in human blood are due to the presence or absence of certain chemicals called antigens. Individuals have different types and combinations of these chemicals.
Antigen = Antibody Generating Agent
Antigens are located on the surface of the red blood cells and the antibodies are in the blood plasma.
Blood Group AIf you belong to blood group A, you have A antigens on the surface of your red blood cells
Blood Group BIf you belong to blood group B, you have B antigens on the surface of your red blood cells
Blood Group ABIf you belong to blood group AB, you have both A and B antigens on the surface of your red blood cells
Blood Group OIf you belong to blood group O, you have no antigens on the surface of your red blood cells
Blood Group Notation
According to the above blood grouping systems you can belong to any of the
following 8 blood groups
A Rh+A RH-
B Rh+B Rh-
AB Rh+AB Rh-
O Rh+O Rh-
Blood transfusionswho can receive blood from whom?
Type O is the universal donorIt has no antigens, so will not start the production of any antibodies.
However, an O recipient can only accept blood from an O donor.
Type A can donate to other type As, but can also donate to type AB.
Type A can accept blood from other type As but also from a type O donor
Type B can donate to other type Bs but can also donate to type AB.
Type B can accept blood from other type Bs but also from a type O donor
Type AB can only donate to other type ABs.
However, Type AB can accept any type of blood (universal acceptor).
DonorType O A B AB
Receiver
O
A
B
AB
Donating blood – The Rh factor
The Rh factor on the red blood cell's surface is also an antigen. Those who have it are called Rh+. Those who haven't are called Rh-.
Source : http://nobelprize.org/educational_games/medicine/
Blood Typing1. Place a drop of the blood sample in each well of the blood typing slide.
Replace the cap on the dropper vial. Note: Always replace cap before opening next vial to prevent contamination.
2. Add a drop of anti-A (Blue) serum to the well labeled A. Replace cap.
3. Add a drop of anti-B (Yellow)anti-B (Yellow) to the well labeled B. Replace cap.
4. Add a drop of anti-Rh (clear) to the well labeled Rh. Replace cap.
5. Using a different color mixing stick for each well (blue for anti-A, yellow for anti-B, white for anti-Rh), gently stir the blood sample and anti-serum drops for 30 seconds. Discard each mixing stick after use to avoid contamination.
6. Carefully examine the thin films of liquid mixture left behind. Observe for:
RESULT Appearance
(-) Film remains uniform in appearance
+ Granules present
Positive result indicates the blood type
7. Record results in the data table. Answer with a YES or NO.
Type A blood
Sample 1 (Demo)
Sample 2 Evan
Sample 3 Stephen
Sample 4
David
Anti-A
Anti-B
Rh
Blood Type
Blood Typing Activity to find out 3 Suspect’s Blood Types
EVIDENCE BLOOD: TYPE O+