FRS 301 Analysis of biological fluids.pptx

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1. FRS 301 1

2. Forensic Science is the application of scientific analysis to law enforcement- Forensic Toxicology, Document examination, Forensic Entomology, etc Every Forensic process starts from the crime scene Branch of forensic science that deals ide nt ifi ca t i o n and an al ysis o f bod i ly f luids - Serology with the Forensic Sero l ogy precedes DN A Analys i s i n a Forens ic Lab 2

3. Around 1900, Karl Landsteiner discovered that there are four different types of human blood based on the presence or absence of specific antigens found on the surface of the red blood cells. This lead to the blood g r oup s A , B, A B and O In 1940, Landsteiner and Weiner reported the discovery of the Rh factor by studying the blood of the Rhesus monkey 3

4. To know how suspected bodily fluids are identified and analyzed in Forensic investigations 4

5. Bodily fluids are liquids that originate from inside the body of humans Blood, Semen , Saliva Blood is the most common Biological stains in the dried state are reasonably stable and can be detected months or years after being deposited 5

6. Is the fluid or stain blood ,semen ,saliva ,etc? Is it of animal or human source? Can it be linked to a particular species or individual? 6

7. Visual/Physical examination- Normally based on the experience of the Analyst. This isn't admissible in a court of law. It can only give a clue to the analyst Presumptive test : This test tells the presence or absence of a suspected fluid. Cannot confirm whether it’s from animal or human. Eg. Blood Confirmatory test : This test gives a high degree of specificity for the body fluid in question. Eg. Human blood 7

8. Use t o visualize hidden s t a ins i n C lothing a nd other materials After detection of stains, presumptive tests can then be performed A dark room is needed 8

9. Some presumptive and confirmatory tests can react to the presence of other substances aside the suspected fluid to give a positive result- False positive Some presumptive and confirmatory tests can give a negative result as a result of the suspected fluid being insufficient for the test- False negative Reagent or kit failure can also give false positive or false negative results to serological tests. This problem can be avoided with testing the reagent or kit on a known bodily fluid ( +ve Control) and a reagent blank ( - ve control) 9

10. Benzidine Colour Test - Benzidine is carcinogenic so not used as often. Benzidine + Blood Stain + Hydrogen peroxide = pink color Kastle-Meyer Colour Test -Phenolphthalein + Bloodstain + Hydrogen peroxide = pink color Luminol Test - Reacts with blood to produce luminescence (glow) Hemastix : use to detect blood in urine but is now widely use to detect blood at the crime scene and in the lab. Reagent strips with TMB (Tetramethylbenzadine) ends.TMB changes from orange to green when it comes into contact with blood 10

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12. Acid Phosphatase Test : Acid phosphatase (AP) is an enzyme secreted by the Prostate gland into seminal fluid Several chemicals detect AP in semen- Alpha Naphthylphosphate: turns purple with semen Fast blue B Dye: turns purple with semen 4-methyl umbelliferyl phosphate: glows with semen contact 400 times AP in semen than any other bodily fluid Reaction time of less than 30 secs. means you have found semen and not any other thing 12

13. Amylase Test : Of the forensic laboratories that perform presumptive testing for saliva, the detection of amylase, an enzyme found at high levels in saliva, is currently the most widely utilized method Amylase is found in a variety of body fluids; saliva, blood, urine, sweat, tears, semen, breast milk, feces, and vaginal secretions , but is more concentrated in saliva Phabedas and Rapid Stain Identification of Human Saliva (RSID™-Saliva) Kits used by many crime labs for presumptive and confirmatory tests 13

14. Jaffe test : Creatinine can serve as a screening test for urine To a drop of stain extract on filter paper, add one drop of Picric acid followed by one drop of 5% Sodium hydroxide. Brown/orange color shows presence of Creatinine 14

15. Pre c ipitin T es t : Combining Hu m an anti s e r um and human blood gives agglutination This principle has been employed in the production of many commercial kits Eg. Hexagon OBTI Kit Requires only small amount of blood Dried blood stains as old as 10 - 15 years work 15

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17. Ele c tro p horet i c Method : H um an an t ibodies and bloodstain are placed in wells on electrophoresis plate Ele c tr i cal cu r rent i s u sed t o m o v e an t ibodies and antigens towards each other If antibodies and antigens move towards each other and form a line of precipitation, it is human blood 17

18. Prostate Specific Antigen (PSA or p30) Test: Prostate- specific antigen, or PSA, is a protein produced by cells of the prostate gland PSA is produced for the ejaculate , where it liquefies semen and allows sperm to swim freely PSA is present in small quantities in the serum of men with healthy prostates 18

19. When PSA is isolated and injected into rabbits, an immune response is triggered which produces antibodies for the PSA (anti-PSA) Serum is then collected from the rabbit Suspected human semen is placed in one well of an electrophoretic plate and anti-PSA is placed in the opposite well When an electric potential is applied, the antigens and antibodies move toward each other Formation of a visible line midway between the two wells shows the presence of human semen. 19

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21. Identification and analysis of various bodily fluids is paramount in the investigation of many crimes Presumptive and confirmatory tests can be performed at the crime scene with the advent of simple-to-use commercial kits 21