Chapter 8 - Blood + Blood Spatter Exam

Aggulation

Clumping of molecules/cells caused by antigen-antibody reaction

Antibodies

Proteins secreted by white blood cells that attach to antigens

Antigens

Any foreign substance/cell in body that reacts w/ antibodies

Antigen-antibody response

Reaction which antibodies attach to specific antigens

Cell-surface protein

Proteins embedded in cell membrane

Lines of convergence

a two-dimensional view of the intersection of lines formed by drawing a line through the main axis of at least two drops of blood that indicates the general area of the source of the blood spatter

Point of origin

a three-dimensional view formed using lines of convergence and angles of impact of at least two different drops of blood to identify the source and location of blood splatter

Red blood cells

donut-shaped cells that carry oxygen throughout the body

Satellite drop of blood

secondary drop formed when some blood breaks free from the main contact drop of blood

White blood cells

cells that police the body by destroying foreign materials

What is the Rh factor?

Type of red cell protein

What does Rh+ indicate?

Blood that has Rh factor

What does Rh- indicate?

Blood that doesn't have Rh factor

ABO blood typing

4 major blood groups based on whether or not you have 2 specific antigens - A & B

Plasma

Liquid platelets and red + white blood cells are suspended in

What dissolved proteins does plasma carry?

Antibodies, hormones, and clotting factors

What nutrients does plasma carry

Glucose, amino acids, salts, minerals

Spines

A bloodstain feature resembling spokes or rays emanating out from the edge of a blood drop; they result from the drop contacting a non-smooth surface.

Blood spatter analysis

uses the shapes and sizes of blood drops to reconstruct the crime scene

Blood spatter patterns

it is possible to determine the direction the blood was traveling, the angle of impact, and the point of origin of the blood.

Types of blood spatter patterns

• Blood falling from 90 degrees

• Arterial spurts/gushes

• Splashes (shaped like !)

• Smears left by bleeding victim (touch)

• Trails of blood from moving victim

• Pools of blood form from victim bleeding heavily + staying in one place

Surface tension

Force that pulls surface molecules of liquid towards its interior

Adhesion

attraction between molecules of different substances

Cohesion

an attraction between molecules of the same substance

Platelets

Aids in blood clotting + involved in repairing damaged blood vessels

ELISA blood test

Lab test used to detect + counts certain antibodies, antigens, proteins, and hormones in bodily fluid samples

Luminol

A chemical that emits a blue glow when it comes in contact with blood

Explain the composition of blood

Plasma, red blood cells, white blood cells, platelets

Describe function of red blood cells

Carries respiratory gases, mainly oxygen + carbon dioxide

• Hemoglobin in red blood cells (iron-containing protein that binds oxygen in lungs + transports oxygen to cells in all tissues of the body) + responsible for color

Describe function of white blood cells

Fight disease + foreign invaders

Describe how to determine the blood type of a sample of blood

• Blood sample is mixed w/ antibodies against type A + B blood.

• Then sample is checked to see if it reacted to one or both of the antibodies

Determine possible weapons based upon high velocity

• less than 1 mm- 100ft/sec- gunshot wound

Determine possible weapons based upon medium velocity

• 1-4 mm 25ft/sec-beating, stabbing

Determine possible weapons based upon low velocity

• 4-6 mm 5ft/sec-blunt object impact

Recreate the crime scene using blood spatter evidence

Direction and angle of the spatter to establish the areas of convergence (the starting point of the bloodshed) and origin (the estimation of where the victim and suspect were in relation to each other when bloodshed occurred).

Explain how and identify chemicals used to assist in locating blood that may no longer be visible

Luminol is reveal these traces with a light - producing chemical reaction, between several chemicals and hemoglobin an oxygen-carrying protein in the blood