Blood is the most common, well-known, and perhaps most important evidence in the world of criminal justice today. There's no substitute for it, whether for medical or forensic purposes. Its presence always links suspect and victim to one another and the scene of violence. Bloodstain patterns tell a lot about position and movement during the crime, who struck whom first, in what manner, and how many times. This destroys most alibi and self-defense arguments for crime, and at the very least, trips most suspects up in their explanation of what happened. Over the years, criminals have tried many ingenious ways to hide, clean up, and remove blood evidence, but it's an area where criminal justice technology has always stayed one step ahead of them.
In the late 1980's, a homicide investigation in a small village in upstate new York involved a girl who was severly beaten on the head with a baseball bat in a poolroom. The floor, pool table, , and ceiling were covered in blood spatter that emanated from the location of the victims head. There were two blockades resulting from the legs of the suspect.. The key to solving this crime was to find the suspect and obtain his pants in order to find the blood spater blockaded at the scene. The suspect was found the same day as the crime. Preliminary tests showed blood on the suspects pants. He claimed it was from a bloody nose during a bar fight, examination of his pant however, revealed that the entire blood spatter consisted of horizontal spatter at a low angle not vetical drops of blood. When confronted with this evidence the suspect addmitted to committing the crime. - The Crime scene: How Forensic Science Works
Characteristics of Blood-
Blood is a mixture of cells (formed elements), enzymes, protiens, inorganic substances (gases), and fluids of course. In unclotted blood plasma is the liquid peice. Plasma makes up approximately 55 percent of the total blood voulume.Formed Elements make up the other 45 percent. Fibrin is also found in plasma. The fibrin strands form a mesh over and open wound to stop bleeding otherwise known as clotting. The SERUM is the liquid that seperates from blood once a clot is formed.
White Blood Cells- These help combat infection.There are several different types of white blood cells; like Platelet(thrombocyte)this plays a role in clotting blood
Red Blood Cells- Transport O2 (oxygen) to and CO2 (carbon dioxide) from cells. Red blood cells are the most numerous blood cells. There are different types of antigens that are on the membrane (outsides) of the red blood cells. Blood Type characteristics are given to Red blood Cells by Blood Antigens. There are 15 major systems. The serologists need to test for antigens to determine compatibility of blood donor and recipient or in some cases victim or criminal or victim(donor) and floor or wall(recipient).
If the serum contains antibodies then it is called antiserum.
For every blood antigen there exists a blood antibody.
"A" blood contains anti B antibody.
"B" blood contains anti A antibody.
"AB" blood contains niether antibody.
"O" blood contains both antibodies.
If an antigen and an antibody combine, this causes agglutination. Because antibodies are bivalent (have 2 reactive sites) they can attach to antigens on two different red blood cells at the same time.
Red blood cells lyse upon drying out, no cells will be in bloodstain but the antigens are still present.
Forensic Serology History.
| Words to know: Plasma-Plasma is made of serum and proteins mixed to the point of solution. Plasma is primarily composed of WATER and makes up approximately 55 percent of the total blood volume. Fibrin- Serum- Antibodies- protiens that destroy or inactivate a specific antigen- immunoglobulins. Agglutination- clumping together of the red blood cells by the action of an antibody.
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