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?

Person of Interest

Forensic Tests (Positive or Negative) Total Positive Results

(Out of 4)Motion Shoe print Finger print Hair Analysis

Ms. Fredericks

Ms. Stewart

Mr. Wislang

Mr. Juteau

Mr. Mulhall

Ms. V.

Gorilla

Summary of Results

Narrowing down our Persons of Interests

Black Blond Red hair hair hair

Who’s blood is it?

XX X

Blood Evidence• Blood samples – Can be analyzed to determine blood

type and DNA, which can be matched to possible suspects.

• Blood droplets – Can be analyzed to give clues to the location of a crime, movement of a victim, and type of weapon.

• Blood spatter – Can be analyzed to determine patterns that give investigators clues to how a crime might have happened.

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

Microscopic Views

Bird Blood

Cat Blood

Dog Blood

Fish Blood

Frog Blood

Snake BloodHuman Blood

Horse Blood

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

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 TYPESBlood 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 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) 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

(-) = NO Film remains uniform in appearance

(+) = YES 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 (Gorilla)

Sample 3 Stewart

Sample 4Ms. V

Sample 5Juteau

Anti-A

Anti-B

Rh

Blood Type

Blood Typing: Results for 4 Suspect’s Blood Types

EVIDENCE BLOOD: TYPE O+

Crime Lab: Blood Analysis Unit Name of Examiner: _____________

Summary of findings: