HOSA FS: Identification of Blood, Bloodstains, Biological Fluids, and Stains

Plasma

The fluid portion of blood that contains the cellular components

Serum

The liquid portion of the blood that remains after clotting

Erythrocytes

Red blood cells that carry oxygen to the tissues that remove carbon dioxide as waste

Leukocytes

White blood cells that defend against foreign substances

Platelets

Important components in clotting and parts of cells

Exsanguination

Bleeding to death

Create little splatter

Hard, smooth surfaces (glass, smooth tile)

Create a lot of splatter

Rough surfaces (wood, concrete)

Narrow end

Part of a blood stain that indicates direction of travel

Area of convergence

2D area in which bloodstain originated, found by using strings to the long axis of blood stains

Area of origin

3D area in which blood stains originated, found by examining the angle of impact and using strings going in the direction of travel at the correct angle

Round stain

Stain that has a 90-degree angle of impact

0.5 w/l stain

Elliptical stain with 30-degree angle of impact

Width/Length

Ratio of discovering angle of impact

Gunshot

Wound that is indicated by back and possibly front spatter and fine misting

Stabbing or beating

Wound with a large spatter around 1-3 mm

Castoff stains

Blood is thrown from a weapon used in a beating ; these stains are typically linear and large

Splashed or projected blood

Large central area with peripheral splatters ; leaves narrow projections

Expirated blood

Mist or spatter of blood due to coughing or vomiting (may contain mucus, be slightly diluted, and contain air bubbles)

Transfer blood stain

Blood stains caused to a clean surface by contact with a surface that is already wet with blood

3-15 minutes

Time it takes for blood to clot

Void

Area with no blood on it while surrounded by blood (indicates that an object has been moved)

Passive blood stains

Blood stains created by gravity acting on blood

Active blood stains

Blood stain due to impact / any force other than gravity

ABO

Classification of blood types based on the reactions of antibodies and antigens

Serology

The laboratory study of body fluids using specific antigen and serum antibody reactions

Agglutination

Process of red blood cells clumping together in response to an antibody

Precipitin test

Test that distinguishes between human and animal blood

Benzidine test

A regent that was once widely used as a presumptive test for blood ; involved using ethanol or acetic solutions which turned blue when the reagent and blood were added

Hemastix test

Commercial test strip that can be used as a presumptive test for blood ; designed to detect blood in urine but also works well in forensics

Phenolphthalein test

A presumptive test for blood that turns pink when blood is added to the reagent

Luminol/Flourescein tests

Presumptive blood test based on chemical reactions that cause light to be emitted from the blood stain

Crystal tests

A type of presumptive test in which a positive result is the formation of a solid crystalline substance

Seminal acid phosphatase

This enzyme is tested for because it is found in abundances in seminal fluid (semen)

Alpha-amylase

Enzyme that is tested for because it is found in saliva (starch-iodide tests are common)

Azostix

A test used to detect urine, or blood in urine (since urine tests are inaccurate and not common in forensic science)

Periodic and Schiff reagent

Presumptive test for the presence of vaginal material ; glycogenated cells are stained bright magenta

Cyanide

A black-colored stomach mucosa is associated with this substance

Barr bodies

Sex can be determined by examining the hair for this chromosome

Lightning

A branching tree on the front of the chest is caused by this phenomenon

Liver

This organ is least likely to be injured by a blast wave