1. Blood & Blood Evidence
Forensic Science 2

2. Function of Blood Functions:
Delivers digested nutrients from fats, proteins and carbohydrates to body cells
Delivers oxygen to all body cells
Delivers chemical messengers to some body cells
Delivers water, minerals and vitamins to cells

3. Functions of Blood Functions
Picks up CO2 waste from cells and carries it to the lungs
Picks up waste from cells and carries it to the kidneys
Moves excess body heat into the skin

4. Blood Facts Ranges in color from a dull red to a scarlet red
About 5 times thicker than water
has a pH between
Temperature runs about °F
Blood is about 8% of body weight
Humans have about 5-6 liters of blood

5. Parts of blood
Parts:
Plasma: mostly water, picks up and delivers nutrients
Red Blood Cells: carry O2 to body cells, red color, has no nucleus, forms in the bone marrow
White Blood Cells: destroys harmful microbes, removes dead cells, helps prevent disease, has a nucleus, also formed in the bone marrow
Platelets: forms blood clots when there is a cut

6. Plasma About 55% of blood Approximately 90% water
Nutrients, respiratory gases, hormones and various wastes are some examples of what is dissolved in plasma
Everyday various organs make dozens of adjustments to maintain the plasma levels

7. Red Blood Cells Called erythrocytes
Main function is to carry oxygen to all the cells in the body
The do not have a nucleus
Hemoglobin is the protein that transfers the oxygen
They are shaped like flattened discs
RBC out number white blood cells by about 1000 to 1

8. White Blood Cells Called leukocytes Protect the body from disease
Account for less than 1% of the blood volume
WBC only use the blood stream to get to their location quickly, but can transport throughout all parts of the body
When an infection is detected the body develop twice the number of WBC in a few hours
A high count of WBC can indicated an infection; however, a low count can also indicate a problem

9. Platelets They are not true cells They are more like “pieces” of cells
They are important for blood clotting

10. Human Blood Groups Blood types: A B AB O
Antigens – recognize foreign substances (stimulates the immune system)
Antibodies – recognizes other body cells

11. ABO Blood Groups

12. ABO Blood Groups

13. Bloodstain Pattern Analysis
What can an investigator learn from the analysis of a blood spatter?
Type and velocity of weapon
Number of blows
Handedness of assailant (right or left-handed)
Position and movements of the victim and assailant during and after the attack
Which wounds were inflicted first
Type of injuries
How long ago the crime was committed
Whether death was immediate or delayed

14. Blood Evidence Collection
Light Source - Investigators will first examine the crime scene to look for areas that may contain blood. They may use a high-intensity light or UV lights to help them find traces of blood as well as other bodily fluids that are not visible under normal lighting conditions.

15. Blood Evidence Collection
Blood Reagent Tests - These tests, referred to as presumptive tests, are used to detect blood at crime scenes based upon the properties of hemoglobin in the blood. Further tests at the crime lab can determine if it is human blood or not.

16. Blood Evidence Collection
Luminol -This chemical is used by crime scene investigators to locate traces of blood, even if it has been cleaned or removed.
Investigators spray a luminol solution is throughout the area under investigation and look for reactions with the iron present in blood, which causes a blue luminescence.
One problem is that other substances also react, such some metals, paints, cleaning products, and plant materials. Another problem is that the chemical reaction can destroy other evidence in the crime scene.
Luminol Reaction

17. Bloodstain Pattern Analysis Terms
Spatter – Bloodstains created from the application of force to the area where the blood originated.
Origin/Source – The place from where the blood spatter came from or originated.
Angle of Impact – The angle at which a blood droplet strikes a surface.

18. Bloodstain Pattern Analysis Terms
Parent Drop – The droplet from which a satellite spatter originates.
Satellite Spatters – Small drops of blood that break of from the parent spatter when the blood droplet hits a surface.
Spines – The pointed edges of a stain that radiate out from the spatter; can help determine the direction from which the blood traveled.
Parent Drop
Spines
Satellite Spatters

19. Types of Bloodstain Patterns
Passive Bloodstains
Patterns created from the force of gravity
Drop, series of drops, flow patterns, blood pools, etc.
Projected Bloodstains
Patterns that occur when a force is applied to the source of the blood
Includes low, medium, or high impact spatters, cast-off, arterial spurting, expiratory blood blown out of the nose, mouth, or wound.
Transfer or Contact Bloodstains
These patterns are created when a wet, bloody object comes in contact with a target surface; may be used to identify an object or body part.
A wipe pattern is created from an object moving through a bloodstain, while a swipe pattern is created from an object leaving a bloodstain.