Forensic Science: Fundamentals & Investigations, 2e Chapter 8 1 All rights Reserved Cengage/NGL/South-Western © 2016

Forensic Science: Fundamentals & Investigations, 2e Chapter 8 All rights Reserved Cengage/NGL/South-Western © 2016 Chapter 8 Blood and Blood Spatter By the end of this chapter you will be able to: 8.1 Describe the forensic significance of the different types of blood cells. 8.2 Summarize the history of the use of blood and blood-spatter analysis in forensics. 8.3 Outline the procedure used to determine blood type. 8.4 Describe how to screen for the presence of human blood. 8.5 Calculate the probability of a person having a specific blood type, using data from population studies. 2

Forensic Science: Fundamentals & Investigations, 2e Chapter 8 All rights Reserved Cengage/NGL/South-Western © 2016 Chapter 8 Blood and Blood Spatter By the end of this chapter you will be able to: 8.6 Describe the proper procedures for handling blood evidence. 8.7 Analyze blood-spatter evidence using angle of impact, areas of convergence, and area of origin. 8.8 Compare and contrast different types of blood-spatter patterns. 8.9 Describe how different types of blood-spatter patterns are formed. 3

Forensic Science: Fundamentals & Investigations, 2e Chapter 8 All rights Reserved Cengage/NGL/South-Western © 2016 o agglutination o angle of impact o antibodies o antigen o antigen-antibody response o area of convergence 4 Chapter 8 Vocabulary o area of origin o cast-off pattern o passive drop o satellite o spine o swipe o wipe

All rights Reserved Cengage/NGL/South-Western © 2016 Forensic Science: Fundamentals & Investigations, 2e Chapter 8 All rights Reserved Cengage/NGL/South-Western © History of the Study of Blood

All rights Reserved Cengage/NGL/South-Western © 2016 Forensic Science: Fundamentals & Investigations, 2e Chapter 8 All rights Reserved Cengage/NGL/South-Western © Composition of Blood

Forensic Science: Fundamentals & Investigations, 2e Chapter 8 All rights Reserved Cengage/NGL/South-Western © 2016 Blood Cells o Red blood cells carry respiratory gases. Oxygen and carbon dioxide o White blood cells fight disease and foreign elements. o Platelets aid in blood clotting and help repair damaged blood vessels. 7

All rights Reserved Cengage/NGL/South-Western © 2016 Forensic Science: Fundamentals & Investigations, 2e Chapter 8 8

All rights Reserved Cengage/NGL/South-Western © 2016 Forensic Science: Fundamentals & Investigations, 2e Chapter 8 9

All rights Reserved Cengage/NGL/South-Western © 2016 Blood Types and Forensics o Blood type provides class evidence. o In 1901, Carl Landsteiner described the A and B antigens in blood. o The Rh factor was identified later. 10

Forensic Science: Fundamentals & Investigations, 2e Chapter 8 All rights Reserved Cengage/NGL/South-Western © 2016 A and B Antigens 11 o The percentage of the US population with each of the four ABO blood types: Type O (43%) Type A (42%) Type B (12%) Type AB (3%)

Forensic Science: Fundamentals & Investigations, 2e Chapter 8 All rights Reserved Cengage/NGL/South-Western © 2016 RH Factor o Eighty-five percent of the human population has a protein called Rh factor on their red blood cells. 12

Forensic Science: Fundamentals & Investigations, 2e Chapter 8 All rights Reserved Cengage/NGL/South-Western © 2016 Antigen-Antibody Response o The antigen-antibody response occurs when white blood cells recognize a substance as foreign and try to destroy it. 13

Forensic Science: Fundamentals & Investigations, 2e Chapter 8 All rights Reserved Cengage/NGL/South-Western © 2016 Agglutination o If agglutination occurs within the circulatory system of a person receiving a blood transfusion, blood could cease to flow. o Without blood circulation, a person dies. 14

Forensic Science: Fundamentals & Investigations, 2e Chapter 8 All rights Reserved Cengage/NGL/South-Western © 2016 Blood-Typing Tests o Prior to a blood transfusion, the patient's blood type needs to be determined. o The patient's blood is tested for the presence of 3 antigens: A, B, and Rh 15

Forensic Science: Fundamentals & Investigations, 2e Chapter 8 All rights Reserved Cengage/NGL/South-Western © 2016 Probability and Blood Types 16

Forensic Science: Fundamentals & Investigations, 2e Chapter 8 All rights Reserved Cengage/NGL/South-Western © 2016 Blood-Spatter Patterns 17

Forensic Science: Fundamentals & Investigations, 2e Chapter 8 All rights Reserved Cengage/NGL/South-Western © 2016 Blood-Spatter Patterns (continued) 18

Forensic Science: Fundamentals & Investigations, 2e Chapter 8 All rights Reserved Cengage/NGL/South-Western © 2016 Directionality of Blood 19 o The shape of an individual drop of blood provides clues to the direction from where the blood originated.

All rights Reserved Cengage/NGL/South-Western © 2016 Forensic Science: Fundamentals & Investigations, 2e Chapter 8 20

All rights Reserved Cengage/NGL/South-Western © 2016 Forensic Science: Fundamentals & Investigations, 2e Chapter 8 All rights Reserved Cengage/NGL/South-Western © 2016 Area of Convergence 21 o The area of convergence is where the blood originated.

All rights Reserved Cengage/NGL/South-Western © 2016 Forensic Science: Fundamentals & Investigations, 2e Chapter 8 All rights Reserved Cengage/NGL/South-Western © 2016 Angle of Impact Calculations o The area of origin is the location of the blood source as viewed in three dimensions. It is determined by projecting angles of impact of individual bloodstains. 22

Forensic Science: Fundamentals & Investigations, 2e Chapter 8 All rights Reserved Cengage/NGL/South-Western © 2016 Calculating the Angle of Impact 1.Measure the width and length of each droplet of blood in millimeters. 2.Divide the width by the length. 3.Take the arcsine, or inverse sine, of the ratio width : length to determine the angle of impact. You can find this decimal value by using a sine table, a calculator, or a computer. 23

All rights Reserved Cengage/NGL/South-Western © 2016 Forensic Science: Fundamentals & Investigations, 2e Chapter 8 All rights Reserved Cengage/NGL/South-Western © 2016 Calculating the Angle of Impact (continued) 24

All rights Reserved Cengage/NGL/South-Western © 2016 Forensic Science: Fundamentals & Investigations, 2e Chapter 8 All rights Reserved Cengage/NGL/South-Western © 2016 Blood Velocity and Spatter Size 25

Forensic Science: Fundamentals & Investigations, 2e Chapter 8 All rights Reserved Cengage/NGL/South-Western © 2016 Crime-Scene Investigation of Blood o Confirmation of the presence of human blood requires detecting human antibodies in the sample. o An ELISA test (Enzyme-Linked Immunosorbent Assay) involves an anti- body-protein reaction. 26

Forensic Science: Fundamentals & Investigations, 2e Chapter 8 All rights Reserved Cengage/NGL/South-Western © 2016 o Blood consists of cellular components and plasma containing dissolved ions, proteins, and other substances. o Blood types result from the presence of antigens on the surface of red blood cells and vary among individuals. Although considered class evidence, blood type is used today to exclude suspects. o Blood-spatter analysis can be used to help recreate a crime scene. 27 Summary

Forensic Science: Fundamentals & Investigations, 2e Chapter 8 All rights Reserved Cengage/NGL/South-Western © 2016 o The size and shape of bloodstains provide clues to the directionality, speed, and angle of impact. o The angle of impact is calculated as the inverse sine of (width/length). o Lines of convergence are used to determine the source of blood in a two-dimensional view. o The characteristics of blood drops on surfaces can show the direction of blood movement and the location of the source of blood and indicate the nature of the wound producing the blood. 28 Summary (continued)

Forensic Science: Fundamentals & Investigations, 2e Chapter 8 All rights Reserved Cengage/NGL/South-Western © 2016 o Investigators can use Luminol to reveal hidden blood spatter. Chemical tests can confirm that the blood found is human. o Characteristic blood-spatter patterns provide clues to the type of injury incurred, along with a possible weapon used to deliver the injury. o Blood-spatter analysis provides scientific evidence used to confirm or refute a person’s description of what happened at a crime scene. 29 Summary (continued)