Blood Typing Practice More Blood Notes Forensic Science 12/19/14

Drill Anna has B- blood. John has AB+ blood. Anna has a baby with type A-. John is surprised—can this be his child? Describe mammalian blood, as seen under a microscope. HW:

IWBAT –Define serology –Describe blood droplets and spatter patterns Objectives

Agenda Drill ABO Genetics practice & HW review Serology Notes Closure

ABO Genetics Problems Work on the back of pg. 5 We will review front and back shortly

Serology The term serology is used to describe a broad scope of laboratory tests that use specific antigen and serum antibody reactions. The identity of each of the four A-B-O blood groups can be established by testing the blood with anti-A and anti-B sera. The concept of specific antigen–antibody reactions has been applied to immunoassay techniques for the detection of drugs of abuse in blood and urine.

Heredity and Paternity Paternity testing has historically involved the A-B-O blood typing system, along with blood factors other than A-B-O. Currently, paternity testing has implemented DNA test procedures that can raise the odds of establishing paternity beyond 99 percent.

Antigen-Antibody Reaction When an animal, such as a rabbit or mouse, is injected with an antigen its body will produce a series of different antibodies, all of which are designed to attack some particular site on the antigen of interest. This collection of antibodies is known as polyclonal antibodies.

Forensics of Blood The criminalist must be prepared to answer the following questions when examining dried blood: 1.Is it blood? 2.From what species did the blood originate? 3.If the blood is of human origin, how closely can it be associated to a particular individual? The determination of blood is best made by means of a preliminary color test.

The Tests A positive result from the Kastle-Meyer color test is highly indicative of blood. –Hemoglobin causes a deep pink color. Alternatively, the luminol test is used to search out trace amounts of blood located at crime scenes. –Produces light (luminescence) in a darkened area. Microcrystalline tests, such as the Takayama and Teichmann tests, depend on the addition of specific chemicals to the blood so that characteristic crystals will be formed.

The Tests Once the stain has been characterized as blood, the precipitin test will determine whether the stain is of human or animal origin. The precipitin test uses antisera normally derived from rabbits that have been injected with the blood of a known animal to determine the species origin of a questioned bloodstain.

Once it has been determined that the bloodstain is of human origin, an effort must be made to associate or dissociate the stain with a particular individual. DNA analysis has allowed forensic scientists to associate blood to a single individual.

Stain Patterns of Blood The crime scene investigator must remember that the location, distribution, and appearance of bloodstains and spatters may be useful for interpreting and reconstructing the events that produced the bleeding. Surface texture and the stain’s shape, size, and location must be considered when determining the direction, dropping distance, and angle of impact of a bloodstain.

Forensic Science: Fundamentals & Investigations, Chapter 8 14 Blood Splatter 1939—splatter patterns first formally analyzed by Balthazard Blood may splatter when a wound is inflicted Blood splatter pattern—a grouping of blood stains Patterns help to reconstruct the events surrounding a shooting, stabbing, or beating

Spatter vs. Transfer Caused by blood being acted upon by force, traveling through air until it hits a surface Caused by a blood source coming into direct contact with a surface

Forensic Science: Fundamentals & Investigations, Chapter 8 16 Blood Splatter Analysis Analysis of a splatter pattern can aid in determining the: –direction blood traveled –angle of impact –point of origin of the blood –velocity of the blood –manner of death

Forensic Science: Fundamentals & Investigations, Chapter 8 17 Blood Splatter Analysis Natural cohesiveness of blood

Forensic Science: Fundamentals & Investigations, Chapter 8 18 Blood Splatter Analysis 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

Effect of surface texture Smooth surface – bloodstain has smooth edges Rough or textured surface – bloodstain has jagged edges

Determining direction of travel

Determining angle of impact width length

Determining the source

Forensic Science: Fundamentals & Investigations, Chapter 8 23 Blood Splatter Analysis Lines of convergence—two or blood splatters can pinpoint the location of the blood source

Determining the source Area of convergence

Forensic Science: Fundamentals & Investigations, Chapter 8 25 Blood Splatter Analysis —Six Patterns Describe each of these: a) Passive drops b) Arterial gushes c) Splashes d) Smears e) Trails f) Pools

Forensic Science: Fundamentals & Investigations, Chapter 8 26 Blood Splatter Analysis —Impact Patterns can help investigators determine the type of weapon used What kind of a pattern is produced by a gun shot? What kind of a pattern is produced by a hammer blow?

Forensic Science: Fundamentals & Investigations, Chapter 8 27 Crime Scene Investigation of Blood 1. Search for blood evidence 2. Determine a. Is the evidence blood? b. Is the blood human? c. What is the blood type? 3. Interpret the findings: a. Does the blood type match a suspect’s blood? b. If not, exclude that suspect c. If yes, decide if DNA profiling is necessary

Closure Siblings are have blood that is A+ and B-. Create parents that make that possible.