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Forensic Chemistry. FOUR TEST FOR BLOOD. 1) PRELIMINARY TEST Determines whether stain is blood or another substance. 2) CONFIRMATORY TEST Confirms the result of the preliminary test; Conclusively identifies substance as blood. 3)PRECIPITIN TEST

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Forensic Chemistry


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  1. Forensic Chemistry

  2. FOUR TEST FOR BLOOD 1) PRELIMINARY TEST • Determines whether stain is blood or another substance. 2)CONFIRMATORY TEST • Confirms the result of the preliminary test; • Conclusively identifies substance as blood.

  3. 3)PRECIPITIN TEST • Determines of blood is of human or animal origin. • If human blood, there appears a white ring in the tube. 4)BLOOD GROUPING TEST • Determines the blood group, if human blood. PRELIMINARY TEST FOR BLOOD 1) BENZIDINE TEST • If positive, the result is PINK.

  4. 2)PHENOLPHTHALEIN TEST • If positive, the result is BLUE. • When exposed to ammonia fumes, it gives off PINK. 3)GUAIACUM TEST 4)LEUCOMALACHITE GREEN TEST 5)LUMINOL TEST

  5. TAKAYAMA TEST- CONFIRMATORY TEST FOR BLODD • If positive, haemocromagen crystals will be produced. • Color of the crystals is SALMON PINK. • Shape of the crystals is RHOMBIC. FOUR BLOOD GROUPS 1)TypeA 2)TypeB 3)TypeAB- rarest blood type 4)TypeO – the most common blood type

  6. PARENTS POSSIBLE NON- OFFSPRING POSSIBLE OFFSPRING OXO O A,B,AB AXO A,O B, AB AXA A,O B, AB BXO B,O A, AB BXB B,O A, AB AXB O,A,B,AB NONE ABXO A,B,AB O ABXA A,B,AB O ABXB A,B,AB O ABXAB A,B,AB O

  7. DNA • stands for DEOXYRIBONUCLEIC ACID • functionally, it is the hereditary material that contains the genetic information necessary for the duplication of cells and for the production of proteins. • chemically, it is an acid, containing deoxyribose sugar and contains four bases: a) A-adenine b) T-thymine c) C-cytosine d) G-guanine • Structurally, it is a double-helix composed of two complimentary strands. • All cells in the body have the same DNA composition.

  8. ALEX JEFFREYS • British molecular biologist who first recognized DNA analysis as having application to forensic science. ADVANTAGES OF DNA IN HUMAN IDETIFICATION 1) it is stable- it can be isolated from a material even after a long period of time. 2) DNA can be examined from a wide variety of biological resources. 3) DNA can be replicated in the laboratory through the process of POLYMERASE CHAIN REACTION(PCR). 4) DNA shows greater variability from one individual to the next.

  9. GENE • Unit of heredity • Complex chemical units contained in the chromosomes • Carries of heredity CHROMOSOMES • Microscopic rod-shaped bodies bearing the genes which carries the traits for transmission • Every normal individual has 46 pairs of chromosomes POLYMERASE CHAIN REACTION(PCR) • a technique for replicating or copying a portion of a DNA strand outside a living cell.

  10. FOUR EXAMINATIONS OF SEMEN AND SEMINAL STAIN 1)PHYSICAL EXAMINATION 2)CHEMICAL EXAMINATION a) Florence Test – Positive result: crystals of cholineperiodide which are dark brown, rhombic or needle shape b) Barberio’s Test - slender yellow tented c) Acid Phosphatase Test 3) MICROSCOPIC EXAMINATION • to determine the presence of spermatozoa 4) BIOLOGICAL EXAMINATION

  11. CHARACRERISTIC PATTERNS OF SURFACE HIT BY FIREARM 1)SINGEING • The slight burning of clothing or the skin around the bullet hole 2)SMUDGING • The blackening of the area surrounding the bullet hole 3)TATTOING • The individual specks of nitrates and nitrites around the bullet hole visible to the naked eye 4) PRESENCE OF NITRITES • Can be determined when paraffin test is conducted

  12. DISTANCE OF FIRING • 0 to 2 inches ( contact firing) – there is the presence of all the characteristic patterns • 2 to 6 inches – there is singeing, smudging, tattooing and presence of nitrates • 6 to 12 inches – there is smudging, tattooing and presence of nitrates • 12 to 36 inches – there is tattooing and presence of nitrates

  13. PARAFFIN TEST • The taking of the cast to extract the nitrates embedded or implanted on the skin. • Must be done within seventy-two(72) hours or three days. Diphenylamine(DPA) Test- Dermal nitrate or lunge DPA Test • Determines the presence and distribution through the use of the Diphenylamine reagent; the chemical aspect of the test POSITIVE RESULT • Minute specks of blue in color will appear when positive for nitrates • On hands, the nitrate appears greenish-blue when dropped with diphenylamine reagent • 3 Problems that arise in the investigation of crime involving firearms: 1)Determination of whether a person fired a gun w/ barehands. 2)Determination of probable gunshot range(distance of firer to the victim) 3)Determination of approximate time of firing of the gun

  14. DANGEROUS DRUGS • MARIJUANA • Commonly called “grass”, Ganja” “tsongki”, “bhang”, “damo” • Botanical name is cannabis sativa L(Linn) • Has three major components: 1)Tetrahydrocannabinol(THC) – purple; the most active alkaloid ; the one causing the hallucinogenic effects 2)Cannabinol – red (physiologically inactive) 3)Cannabidiol – pink (physiologically inactve) pharmacological classificatitonis hallucinogen

  15. LEGAL DEFINITION OF MARIJUANA • The term marijuana as defined by law means all parts of the plant whether growing or not, the seeds thereof, the resin extracted from any parts of such plant, every compound, manufactured, salt derivative, mixture or preparation of such plant, it seeds or resin.

  16. KINDS OF EXAMINATION FOR MJ 1)MICROSCOPIC 2) CHEMICAL 3)THIN LAYER CHROMATOGRAPIC • Confirmatory test for mj • Makes use of test plate which is soaked in a solvent system for one (1) hour • If positive, spots will appear • Said spots are the active ingredient of mj

  17. CHEMICAL SOLUTION FOR EXTRACTING THE RESIN OF MJ 1)Chloroform 2)Methanol 3)Ethel TESTING THROUGH THE USE OF IMPREGNATED FILTER PAPER SOAKED IN SODIUM HYDROXIDE (NaOH) • If positive, there appears a spot purple red • If negative, there appears scattered purple color

  18. PARTS OF HAIR 1)ROOT • Portion embedded in the skin 2)SHAFT • Portion above the surface of the skin • The most distinctive part 3)TIP • The distal end of an uncut hair shaft PARTS OF SHAFT 1)CUTICLE - outermost covering of the hair 2)MEDULLA- center of the hair structure 3)CORTEX • the intermediate and the thickest layer of the shaft • Composed of elongated spindle-shaped fibrils

  19. TEST FOR TEXTILE FIBERS 1)Burning or Ignition Test • a simple preliminary examination • Determines whether fiber is mineral, animal or vegetable 2)FLUORESCENCE TEST • Determines the general group to which a fiber belongs • However, it is not reliable for positive identification of fiber 3)MICROSCOPIC EXAMINATION • The most reliable and best means of identifying fiber

  20. End of Discussion Good Day!