1

Learning Objectives

Explain blood biochemistry and blood typing

Conduct blood spatter analysis to find the

source of blood and reconstruct past events

Identify the various blood spatter patterns

1

3

4

Describe the methods used in the

identification and individualisation of blood

2

2

Blood

Fresh

Old & dried

Obvious

Obvious?

3

Whose blood is it?

Show up invisible stains

Is it blood?

1

3

Is it human blood?

Can we use blood spatter

patterns to reconstruct events?

4

2

Blood

4

Blood Composition

Fresh frozen

blood plasma

Fluid portion of blood

55% by weight

Transport system

8% of body weight

Blood plasma

5

Blood Composition

Left to right: erythrocyte,

thrombocyte, leukocyte

Blood cells

Oxygen transport

Red blood cells / erythrocytes

8% of body weight

Blood plasma

6

Blood Composition

Left to right: erythrocyte,

thrombocyte, leukocyte

White blood cells / leukocytes

Immune response

Blood cells

Red blood cells / erythrocytes

8% of body weight

Blood plasma

7

Blood Composition

Left to right: erythrocyte,

thrombocyte, leukocyte

Clotting response

Platelets / thrombocytes

White blood cells / leukocytes

Blood cells

Red blood cells / erythrocytes

8% of body weight

Blood plasma

8

Erythrocytes

7.8 microns in diameter

No nucleus

Biconcave

No DNA

Red blood cell

9

Erythrocytes

Principal function

4 oxygen molecules

on each protein

Oxygen transport

Red blood cell

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Antigens

Proteins on surface of red blood cells

Over 100 rare antigens

30 commonly occurring antigens

Responsible for blood typing

11

Blood transfusion

Must be given blood of the right type

Early days

Some people fine after

a blood transfusion

Some people fell ill or died

after a blood transfusion

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Karl Landsteiner

Karl Landsteiner

Developed the A-B-O

blood typing system

Won the 1930 Nobel

Prize in Medicine

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A-B-O Blood Types

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A-B-O Blood Types

Occurrence of blood types vary

Blood Type Percentage (%)

O

40

A

25

B

30

AB

5

15

Blood Types & Personality

No

Is your blood type

the key to true love?

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Blood Types & Personality

“I am type B and

have the tendency

to be simplistic and

straightforward at

times.”

- Ryu Matsumoto

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Antibodies

20% of blood

plasma volume

Immunoglobins

Produced as part of

immune response

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Antibodies

Antigen binding sites

Bind to “alien” objects

Extremely specific

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Serum Antibodies

Antibodies corresponding to surface antigens

Anti-A antibodies

Anti-B antibodies

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A-B-O Blood Types

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Blood typing system

Many different antigens

A-B-O system based on A and B antigens

Less common antigens

D antigen / rhesus antigens

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Rhesus antigens

Rhesus

positive

With D antigen

Without D antigen

Rhesus

negative

85% of population

15% of population

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Blood Type Distribution in Singapore

Blood Type Percentage (%)

O+

34

O-

6

A+

21

A-

4

B+

25.5

B-

4.5

AB+

4

AB-

1

Want to individualise

evidence

Blood types are

not individualised

24

Bio-Identification

Individualisation of blood type?

More complex blood typing

Inferior to DNA fingerprinting

Blood sample

Individualise it

Extensive research before 1990

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Bio-Identification

Cannot be used to prove guilt

Can be used to establish innocence

Blood type not individualised

26

Bio-Identification

Crime scene

Type A blood found

Established innocence

Suspect is type B blood

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Bio-Identification

Does not prove guilt

Suspect is type A blood

Require further evidence

Crime scene

Type A blood found

Suspect is type B blood