1. Blood & Blood Spatter
Mr. Davis

2. Blood
Blood is a circulating tissue consisting of three types of cells:
red blood cells
white blood cells
platelets
These cells are suspended in a liquid known as plasma. Plasma is similar to salt water in composition. It carries dissolved proteins, such as antibodies, hormones, and clotting factors, and nutrients such as glucose, amino acids, salts, and minerals.

3. Blood Blood typing provides class evidence
DNA profiling provides individual evidence
A blood splatter pattern provides information
the truthfulness of an account by a witness or a suspect
the origin of the blood
the angle and velocity of impact
the type of weapon used

4. Basic Components of Blood
Plasma—a liquid suspending other blood components
Red blood cells (Erythrocytes)— carries oxygen to the body’s cells and carbon dioxide away
White blood cells (Leukocytes)— fights disease and foreign invaders and, alone, contain cell nuclei
Platelets—aids in blood clotting and the repair of damaged blood vessels

5. Components of Blood
Red blood cells (erythrocytes) carry respiratory gases, mainly oxygen and carbon dioxide.
The hemoglobin in red blood cells is an iron- containing protein that binds to oxygen in the lungs and transports the oxygen to cells in all the tissues in the body. Hemoglobin in red blood cells is also responsible for the red color in blood.
White blood cells (leukocytes) fight disease and foreign invaders.
Platelets (thrombocytes) aid in blood clotting and are involved in repairing damaged blood vessels.

6. Components of Blood

7. When the immune system recognizes the presence of invading foreign molecules, white blood cells, which migrate throughout the body, concentrate in the location of the invading material—whether it is a virus, bacteria, or protein. The white blood cells engulf and digest the invader. Other white blood cells secrete proteins, known as antibodies, which assist in the immune response.
Immune Response

8. Antibodies are Y-shaped proteins secreted by white blood cells that attach to antigens to destroy them
Antigens are foreign molecules or cells that react to antibodies
Enzymes are complex proteins that catalyze different biochemical reactions
Many enzymes and proteins have been found in the blood that are important for identification purposes

9. agglutination the clumping of molecules or cells caused by an antigen–antibody reaction.
 antibodies proteins secreted by white blood cells that attach to antigens.
 antigen–antibody response a reaction in which antibodies attach to specific antigens.
 antigens any foreign substance or cell in the body that reacts with antibodies.
 cell-surface protein proteins embedded in the cell membrane.

10. Basics of Blood

11. Blood Stains
When bloodstains are studied with respect to their geometry and distribution on various surfaces, they can reveal valuable information for the reconstruction of events that produced the bloodshed.
Origin(s) of the bloodstains
Distances between target surface and origin at time of bloodshed
Type and direction of impact that produced bloodstains
Object(s) that produced bloodstain patterns
Number of blows, shots, etc. that occurred

12. Blood Stains
Position of victim, assailant, or objects during bloodshed
Movement and direction of victim, assailant or objects after bloodshed
Support or contradiction of version of events given by suspect or witnesses
Additional criteria for estimation of time of death
Correlation with other laboratory and pathology findings relevant to an investigation

13. Blood Spatter
Blood Spatter is categorized as impact spatter (created when a force is applied to a liquid blood source) or projection spatter (caused by arterial spurting, expirated spray or spatter cast off an object).
The characteristics of blood spatter depend on the speed at which the blood leaves the body and the type of force applied to the blood source.

14. Blood Spatter Satellite droplets—
When blood falls from a height, or at a high velocity, it overcomes its natural cohesiveness, and separates from the main droplet
Spiking patterns—
Form around the droplet edges when blood falls onto a less-than-smooth surface

15. Gunshot spatter
includes both forward spatter from the exit wound and back spatter from the entrance wound.
Gunshot spatter will vary depending on the caliber of the gun, where the victim is struck, whether the bullet exits the body, distance between the victim and the gun and location of the victim relative to walls, floors and objects.
Typically, forward spatter is a fine mist and back spatter is larger and fewer drops.

17. Cast-off
Cast-Off results when an object swung in an arc flings blood onto nearby surfaces.
This occurs when an assailant swings the bloodstained object back before inflicting another blow.
Analysts can tell the direction of the impacting object by the shape of the spatter (tails point in the direction of motion).
Counting the arcs can also show the minimum number of blows delivered.

21. Arterial spray
Arterial Spray - refers to the spurt of blood released when a major artery is severed.
The blood is propelled out of the breached blood vessel by the pumping of the heart and often forms an arcing pattern consisting of large, individual stains, with a new pattern created for each time the heart pumps.

23. Expirated spatter
Expirated Spatter - is usually caused by blood from an internal injury mixing with air from the lungs being expelled through the nose, mouth or an injury to the airways or lungs. Expirated spatter tends to form a very fine mist due to the pressure exerted by the lungs moving air out of the body. Small air bubbles in the drops of blood are typically found in this type of spatter.

26. Blood Spatter
Passive Bloodstains - Patterns created from the force of gravity; can be a single 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, and expiratory blood blown out of the nose, mouth, or wound.
Transfer or Contact Bloodstains - The pattern created when a wet, bloody object comes in contact with a target surface; may be used to identify an object or body part.

27. Types of Blood Stain Patterns
Bloodstains are classified into three basic types: passive stains, transfer stains and projected or impact stains.
Passive stains include drops, flows and pools, and typically result from gravity acting on an injured body.
Transfer stains result from objects coming into contact with existing bloodstains and leaving wipes, swipes or pattern transfers behind such as a bloody shoe print or a smear from a body being dragged.
Impact stains result from blood projecting through the air and are usually seen as spatter, but may also include gushes, splashes and arterial spurts.
Types of Blood Stain Patterns

28. Passive Blood Stains

29. Projected Blood Spatter

30. Impact Blood Spatter

31. Transfer Blood Spatter

32. Angle of Impact
The bottom of the spatter stain will be more dense than the top of the stain.

33. Trigonometry and Angle of Impact
To determine the angle of impact:
Measure the width and length of the blood spatter. Length must be longer than width.
Divide width by length.
Take the arcsine of your result.
This formula will not produce accurate results at extreme angles ( less than 10˚ or greater than 60 ˚).
𝑠𝑖𝑛𝜃= 𝑤 𝑙
𝜃=arcsine 𝑤 𝑙

34. Area of Convergence (2d area)
To determine the area of convergence, investigators calculate the direction and angle of many blood stains.
For each blood stain analyzed, they place a string at the stain which is parallel to the angle of the blood droplet.

35. Area of Convergence (2d area)
After many strings have been placed, a general area of convergence will appear where the strings overlap.
This can also be done on a computer with image analysis software.

36. Lines of convergence—two or more blood spatters can pinpoint the location of the blood source*

37. Blood spatter Analysis - Angle of Impact
Using elastic string, the analyst draws lines from each spatter through the level line. Then, he or she uses a protractor on the level line in the area where the strings converge to determine the angle of flight for each spatter. If the spatters are mostly on a wall, the analyst can measure the distance from the area of convergence to the wall to find out where the victim was located.
First, the analyst has to locate each spatter and measure its length and width using a scale, a ruler or calipers. Then, he or she computes the angle using this formula:
angle of impact = arcsin (opposite side/hypotenuse) *

38. 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 as some metals, paints, cleaning products, and plant materials. Another problem is that the chemical reaction can destroy other evidence in the crime scene.

40. Luminol

41. Fluorescein
This chemical is also capable of detecting latent or old blood, similar to luminol. It is ideal for fine stains or smears found throughout a crime scene. After the solution has been sprayed onto the substance or area suspected to contain blood, a UV light and goggles are used to detect any illuminated areas, which appear greenish-white if blood is present. It may also react to many of the same things as luminol (copper and bleach).

42. Fluorescein

43. Leuco-crystal Violet reacts with the heme-group in blood to give a violet color. Its application can be used to identify bloodstains that are not visible and to enhance and provide additional contrast to bloodstain patterns that are visible.  This reagent contains hydrogen peroxide, so if used on heavy bloodstains foaming may result and cause loss of detail. 
Leuco-crystal violet is typically used on porous surfaces. Leuco-crystal Violet reacts with heme, and therefore is a presumptive test for blood. 
However, it is NOT the presumptive test for blood used by the Laboratory.  Presumptive testing for blood is done using phenolphthalein reagent.

47. Presumptive Blood Test

48. Hema Sticks