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Unformatted text preview: Forensic Science
•Identify the Victim/Remains •Identify the Criminal (Murderer/Rapist…) Evidences for Courts Evidence Physical identification Chemical identification Biological identification Forensic Pathology •Who is the victim? •What injuries are present? •When did the injuries occur? •Why and how were the injuries produced? Forensic Odontology -Teeth examination -Facial reconstructions Collecting the evidence
Remains (Age, possible cause of death) Hammer Clothes Red/White/Blue Bag Van – Fingerprints? - Blood Stains - First Crime Scene? Forensic Biology What are useful biological materials? Forensic Serology A Bloody Mess Find a Stain at a Crime Scene •Is it Blood? •Is it from human or not? •Blood Typing - A, B, AB, O Is it blood? • Presumptive test - very sensitive - can have false positive • Confirmatory test - not as sensitive - specific Presumptive test 1. Phenolphthalein color test
- based on peroxidase activity of hemoglobin Fe3+[heme]+ H2O2 → H2 + [O] → color
- turns pink if it is blood, remain colorless if blood is not present Non-Human Blood? 2. Hemastix ® strips
Detection of heme of hemoglobin Blood? Non-Human Blood? 3. Luminol – Fluorescent blood detector How does Luminol detect blood?
Reacts with heavy metals to glow in the dark. e.g. iron, copper, chlorine H2O2 + AH2 2H2O + A Fe in Heme Even at areas cleaned after a murder! Confirmatory Tests
Takayama and Teichmann tests Chemicals that form crystals with hemoglobin Highly specific Examine under microscope If it is blood, is it human blood? Test sample Rabbit serum that has been sensitized to human blood. Anti- Anti- • Precipitin test antigen + antibody = precipitate •Species Identification tests (Ouchterlony Gel) OK! So it is human blood! But, so ? Blood groups? The Nature of Blood
1. Plasma (55%) 2. Blood solids Red blood cells White blood cells Platelets • In 1901 Dr. Karl Landsteiner A - A antigen only 40-42% population B - B antigen only 10-12% population AB - Both A and B antigens 3-5% population O - Neither antigen 43-45% population Antibody and Agglutination - Human Blood group determination ⇐ Microscopic view of normal red blood cells Microscopic view of agglutinated red blood cells ⇒ Other proteins in Blood: - Rh factor - 85% population - Polymorphic enzymes Phosphoglucomutase PGM1 – 58% PGM2 – 6% PGM2-1 – 36% Adenosine deaminase Haptoglobin Transferrin ……………. Matching of Blood Type and Isozymes
What is the possibility of a suspect’s blood sample sharing the following characteristics with the blood sample collected at the crime scene ? • • • • Blood Group A Basic subtype A2 Protein AK Enzyme PGM 2 42% 25% 15% 6% Answer: 0.00094 (0.42 X 0.25 X 0.15 X 0.06) or
1 in 1063 Bloodstain patterns Arterial Spurting (or Gushing) Pattern Drip Pattern Swipe Pattern Transfer/Contact Patterns (Of Fingers) Knife blade Footwear (Of Screwdriver) Blood Drops Impact Angles (Jackson & Jachson) Point of Origin (Jackson & Jachson) Low Velocity Impact (LVIS) Medium Velocity Impact (MVIS) High Velocity Impact Spatter (HVIS) Blood is not the only biological samples
Approximately 80% of the population are secretors i.e. antigens, antibodies, proteins and enzymes that characterize their blood are also found in other body fluids like tears, sweat, saliva, vaginal fluids and semen. Crime Scene Investigation
Under blue light, semen, saliva, urine will fluoresce http://www.csigizmos.com/p roducts/portablelightsourc es/microblue.html Presumptive Test for semen
Acid phosphatase in the seminal fluid (also found in vaginal fluid) Confirmatory Test! 1. Presence of prostate specific antigen or p30. 2. Presence of spermatozoa. Monica Lewinsky's blue dress is one piece of supporting evidence in the Starr Report ...
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- Spring '08