8-1 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE An Introduction By Richard Saferstein Chapter 8

8-2 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE An Introduction By Richard Saferstein  Blood is a highly complex mixture of cells, enzymes, proteins, and inorganic substances.  Plasma, is the fluid portion of blood and composed principally of water.  Red blood cells (erythrocytes), white blood cells (leukocytes), and platelets are the solid materials suspended in plasma.  Antigens, (proteins) are located on the surface of red blood cells and are responsible for blood-type characteristics.

8-3 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE An Introduction By Richard Saferstein  More than 15 blood antigen systems have been identified, but the A-B-O and Rh systems are the most important.  An individual that is type A has A antigens on his/her red blood cells, type B has B antigens, AB has both A and B antigens, and type O has neither A nor B antigens.  Rh factor is determined by the presence of another antigen, the D antigen.  People having the D antigen are Rh positive; those not having the antigen are Rh negative.  For every antigen there is a specific antibody that will react with it to form clumps known as agglutination.  Thus, if serum containing anti-B is added to red blood cells carrying B antigen, they will immediately react.

8-4 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE An Introduction By Richard Saferstein  Early transfusions were direct (from one person to another)  90% of tranfusion patients died before transfusion was finished  Landsteiner looked at the blood of failed transfusions and noticed clumping of blood cells  Discovered A-B-O system of surface proteins in FRESH blood  Lattes discovered a way to determine blood type from dried blood  Rh factor named for Rhesus monkey  Other surface proteins include: Minnesota, Lutheran, Kell, HLA

8-5 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE An Introduction By Richard Saferstein  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.

8-6 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE An Introduction By Richard Saferstein  A number of immunoassay techniques are commercially available for detecting drugs through antigen-antibody reaction.  One is Enzyme-Multiplied Immunoassay Technique (EMIT), is speedy and very sensitive detecting drugs in urine.  In EMIT analysis, antibodies that will bind to a specific drug are added to the subject’s urine (Ch 6).  Radioimmunoassay (RIA), use drugs labeled with radioactive tags.

8-7 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE An Introduction By Richard Saferstein  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.  A specific collection of antibodies designed to combine with a single antigen site can be also be made and are known as monoclonals.

8-8 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE An Introduction By Richard Saferstein The criminalist must answer the following three questions when examining suspected bloodstains: 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? Question #1 can be answered by a color test. Presumptive blood test

8-9 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE An Introduction By Richard Saferstein  The Kastle-Meyer color test uses phenolphthalein to detect blood.  Hemoglobin causes a deep pink color.  Luminol test can detect blood diluted up to 300,000 times.  Produces blue glow (luminescence) in a darkened area.  Microcrystalline tests, Takayama and Teichmann, uses chemicals that form crystals if blood is present. Not very sensitive. Easily contaminated. Luminol Test

8-10 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE An Introduction By Richard Saferstein Question # 2:  Precipitin test uses antibodies from rabbits that have been injected with the blood of a known animal to determine the species of a questioned bloodstain. Question #3: if the bloodstain is human, it must be matched to the crime scene, either the victim or suspect(s).  DNA analysis has allowed forensic scientists to match blood to a single individual.  Before 1990’s, ABO blood typing could only be used to eliminate a suspect, but could not be used to convict them.

8-11 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE An Introduction By Richard Saferstein  The location, distribution, and appearance of bloodstains and spatters give useful information for reconstructing the events that produced the blood.  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.

8-12 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE An Introduction By Richard Saferstein  The harder and less porous the surface, the less blood spatter.  The direction of travel of blood striking an object is determined by the pointed end of a bloodstain which always points in the direction of travel.  The impact angle of blood on a flat surface at right angles shows a circular spot, as the angle decreases-the stain becomes more oval.  The origin of a blood spatter in a two-dimensional projection can be established by drawing straight lines through the long axis of several individual drops The intersection or point of convergence of these lines represents the origin point.

8-13 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE An Introduction By Richard Saferstein  The transfer of hereditary material is accomplished by means of units called genes, located on chromosomes.  Alleles: Alternative forms of genes that influence a given characteristic (such as eye color or blood type).  Paternity testing has historically involved the A-B-O blood typing system, along with blood factors such as Rh (D).  DNA test procedures raise the odds of establishing paternity beyond 99%.

8-14 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE An Introduction By Richard Saferstein  Many of the cases sent to a forensic laboratory involve sexual offenses, making it necessary to examine exhibits for the presence of seminal stains.  The best way to locate and at the same time characterize a seminal stain is to perform the acid phosphatase (an enzyme found in seminal fluid) color test.  A purple color indicates acid phosphatase enzyme.  Semen are identified by either the presence of spermatozoa or of p30, a protein unique to seminal plasma.  Forensic scientists can link seminal material to an individual by DNA typing.

8-15 PRENTICE HALL ©2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE An Introduction By Richard Saferstein  WET blood items are collected and packaged in paper to prevent mold and bacteria growth. Wet spots can be collected with sterile dry swabs and packaged in paper.  Dried blood can be collected with a sterile swab and either sterile water or saline solution and packaged in plastic vials or tubes.  Large areas such as bedding or carpeting can be cut to obtain stained AND UNSTAINED control samples  WET items MUST be unpacked at the lab and AIR DRIED in a controlled environment.