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Identification and Characterization of Blood and Bloodstains

Identification and Characterization of Blood and Bloodstains. Serology involves the examination and analysis of body fluids; for purposes of this presentation, blood. Even though DNA analysis is predominant identification method used, many laboratories still utilize serological testing.

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Identification and Characterization of Blood and Bloodstains

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  1. Identification and Characterization of Blood and Bloodstains • Serology involves the examination and analysis of body fluids; for purposes of this presentation, blood. • Even though DNA analysis is predominant identification method used, many laboratories still utilize serological testing

  2. Protocol for Analysis of Blood • Careful visual examination of any item suspected to evidence for the presence of blood • Application of a suitable presumptive screening test • Application of a specific and sensitive test to confirm blood presence • Determination of biological or species origin • Characterization of blood using genetic markers or DNA

  3. Identification of Blood • Initially a presumptive chemical screening test followed by a confirmatory test is done • Presumptive tests allow examiner to: • Confirm blood is present when results are positive • Eliminate stains from further consideration when test is negative

  4. Identification of Blood • Presumptive tests may be recognized as those which produce a visible reaction or result in a release of light • Catalytic color tests use chemical oxidation of a chromogenic substance by an oxidizing agent catalyzed in the presence of blood, specifically hemoglobin

  5. Identification of Blood • Catalytic Color Tests (CCTs) can result in false positive results • Keys to reducing false positives are: • Experience • Careful observation • Routine application of confirmatory tests

  6. Identification of Blood Method of presumptive tests: • Sample a stain with a clean, moistened cotton swab • Adding a drop of reagent • Adding a drop of hydrogen peroxide • Immediate development of color will appear to signify presence of blood

  7. Test type and color result to signify presence of blood Benzidine–Adler Test – blue-dark blue Phenolphthalein–Kastle - Mayer Test - pink 0- Tolidine Test -blue Leucomalchite Green (LNG) - green Tetramethylbenzidine - Hemastix – green – blue green Types of Presumptive Tests

  8. Leucomalachite reactions Phenolphtalein reactions

  9. Tests using Chemiluminescence and Fluorescence • Chemiluminescence – process by which light is emitted as a product of a chemical reaction. No other light is required - Luminol • Fluorescence – occurs when a chemical substance is exposed to a particular wavelength of light (usually short wavelengths- ultraviolet) and light energy is emitted at longer wavelengths

  10. Tests using Chemiluminescence and Fluorescence • When blood presence is suspected, but little is to be seen, luminol and fluorescein may be used. • These are presumptive tests. • Chemical is mixed and sprayed over general area • More easily visible in reduced lighting • Alternate light source is often used • Photographs and sketches should be done

  11. Luminol • Luminol is mixed with oxidant in an aqueous solution • Mixture is sprayed over area • Catalytic activity of the heme group accelerates oxidation of luminol, producing a blue-white to yellowish green light when blood is present • Luminol is extremely sensitive to presence of blood

  12. Fluorescein • Fluorescein works similarly to luminol • Fluorescein which has a commercial thickener can adhere to vertical surfaces • Fluorescein requires use of an alternate light source, which typically is set at 450 nanometers • Fluorescein will not fluoresce with household bleach, while luminol does.

  13. Confirmatory Test for Blood • Several types of confirmatory tests utilize formation of crystals to detect presence of blood. • Types of test include: • Teichmann Test • Takayama Test – more effective than Teichmann test

  14. Takayama crystals Teichmann crystals

  15. Species Origin Determination in Bloodstains • Serum Protein Analysis is used to determine origin of bloodstain • Types of tests: • Ring Precipitin Test • Ouchterlony Double Diffusion Test • Crossed – over Electrophoresis • Anti- Human Hemoglobin • Immunoelectrophoresis • Laurel electrophoresis

  16. simulator

  17. Antigen Based Markers: Blood Groups • ABO system - 1st and best known blood grouping system, discovered by Karl Landsteiner, 1900 • Absorption Elution • Lattes Crust Test • Secretors • The Lewis System • Rhesus System

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