Identification of human and animal blood.pptx

Forensic Medicine: Undergraduate

1. Dr Muhammad Wasif Forensic Med Deptt. Identification of human and animal blood

2. Forensic serology is the application of immunological and biochemical methods to identify the presence of a body fluid or tissue sample. It deals with the investigation of a crime and the possible further genetic characterization of the sample. Introduction to forensic serology

3. Definition Forensic serology thus is the study and examination of body fluids such as blood, semen, sweat, urine, saliva, fecal matter, and other fluids mainly for identification purposes in criminal/ medicolegal investigations .  Blood is the most commonly recovered and one of the most important pieces of evidence utilized in forensic investigations. It is commonly recovered in cases of homicide, assault, and terrorist attacks, including bomb blasts.

4. Blood is the most commonly recovered and one of the most important pieces of evidence utilized in forensic investigations. It is commonly recovered in cases of homicide, assault, and terrorist attacks, including bomb blasts.

5. Blood as evidence holds significance in the criminal justice system as it can link a crime with a criminal or exclude an individual’s involvement in a crime. Moreover, the pattern of blood stains can help in reconstruction of a crime scene by conveying information about the relative position and movement of the criminal and victim at the crime scene. Medical science is more interested in white blood cells, while Forensic science is more interested in red blood cells and serum.

6. In   forensic science ,  Locard's principle  holds that the perpetrator of a crime will bring something into the crime scene and leave with something from it, and that both can be used as  forensic evidence .." LOCARD’S principle of exchange

7. Dr.  Edmond Locard  (1877–1966) was a pioneer in forensic science who became known as the  Sherlock Holmes  of Lyon, France. [1]  He formulated the basic principle of forensic science as: "Every contact leaves a trace ". It is generally understood as "with contact between two items, there will be an exchange

8. Most well known and significant evidence in modern criminal justice system. Because It can link a victim to a suspect ( via Locard’s Exchange Principle) Bloodstain patterns reveal great deal about position and movement during crime. It managed to destroy self defense arguments of suspects. Blood evidence

9. GENERAL CHARACTERISTICS Slightly alkaline fluid Fluid portion of blood consists of plasma and serum Non fluid portion consists of 3 types of blood cells i -e Red blood cells, White blood cells and Platelets. Blood is composed of Water Cells Enzymes Proteins Other organic substances Nature of blood

10. Most prevalent blood cells in the human body Deliver oxygen from the lungs to the body’s tissues Forensic analyst search for smaller chemical substance residing on their surfaces (antigens) which also tend to have important forensic implications Red blood cells

11. Characterized by its yellow hue, and contains white blood cells and platelets Forensic analysts are able to determine the freshness of blood sample by its serum since it clots several minutes after being exposed to air A centrifuge can be used to separate the clotted material from the serum portion Serum contains antibodies, protein floating in the blood fluid which have important forensic implications serum

12. Blood group is a classification of  blood , based on the presence and absence of  antibodies  and  inherited   antigenic  substances on the surface of  red blood cells  (RBCs). These antigens may be  proteins ,  carbohydrates ,  glycoproteins , or  glycolipids , depending on the blood group system. Some of these antigens are also present on the surface of other types of  cells  of various  tissues . Several of these red blood cell surface antigens can stem from one  allele  (or an alternative version of a gene) and collectively form a blood group system . Blood grouping

13. The  ABO blood group system  is used to denote the presence of one, both, or neither of the A and B  antigens  on  erythrocytes The ABO blood types were first discovered by  Karl Landsteiner  in 1900 He found that red blood cells would clump together ( agglutinate ) when mixed in test tubes with sera from different persons, and that some human blood also agglutinated with animal blood Blood group systems

14. Blood typing requires 2 antiserums Anti A serum Anti B serum A blood agglutinated by anti A serum B blood agglutinated by anti B serum AB blood by both O blood by neither Blood typing

15. Rhesus ( Rh ) factor is an inherited protein found on the surface of red blood cells. If your blood has the protein, you're Rh positive. If your blood lacks the protein, you're Rh negative. Rh positive is the most common blood type. The  Rh blood group system  is a  human blood group system . It contains proteins on the surface of red blood cells. After the  ABO blood group system , it is the most likely to be involved in transfusion reactions. The Rh blood group system consists of 49 defined blood group  antigens , among which the five antigens D, C, c, E, and e are the most important. Rhesus factor

16. Five specific questions as guidelines for determining the nature of the crime; Is the sample blood? Is the sample animal blood? If the sample is animal blood, then from which species did it come from? If the sample is human blood, what type is it? Can the sex, age and race of the source of the blood be determined? Blood analysis

17. The task in examination of blood stains is to produce conclusive proof of their origin by carrying out the following examination Physical Chemical Microscopic Serological Identification of stains

18. Naked eye examination Examination under; Dissecting microscope Ultraviolet light Physical examination

19. LUMINOL TEST Forensic scientists spray luminol onto surfaces at crime scenes to detect invisible blood stains. Wherever the luminol touches blood, it glows, and the glow is bright enough to be photographed. Chemical Screening tests

20. PHENOLPHTHALEIN (KastLe- MEYEr’s ) test Phenolphthalein is a presumptive test that reacts with the heme molecule present in blood. A positive reaction gives a pink color . While bloodstains normally appear red-brown in color, the color of the substrate or the age of a stain may affect the appearance or visibility of the stain.  Phenolphthalein tests are typically conducted on suspected bloodstains prior to collection.  While a positive phenolphthalein reaction is indicative of blood, it is only a presumptive test and false positives are possible .   Additionally, the reaction is not species specific.  Positive reactions are not limited to human blood

21. O- TOLIDINE TEST A test for the presence of hemoglobin in feces or urine. The O- Tolidine can be in a solution, in a tablet or impregnated onto an absorbent paper. A positive test is the development of green to blue color. LEUCOMALACHITE GREEN TEST

22. Haemochromogen Crystal Test ( TAKAYAMA TEST ) Micro Chemical Test for Hemoglobin; Spectroscopy Confirmatory chemical test for hemoglobin

23. Preparation of film Staining of the film (Jenner’s Stain) Examination under microscope (Shape, size and presence of nucleus in RBCs) SEX DETERMINATION IN WBCs Slides are stained with Jenner’s Stain and examination of WBCs help determining the sex. Blood must be fresh for this test. WBCs show their feminine trait, a thin stalked drumstick projection of polymorph nucleus given the name DAVIDSON BODY. Microscopic examination (Identification of cells)

24. RACE DETERMINATION Certain racial genetic markers involving protein and enzyme tests can help establish race. AGE DETERMINATION Fetal Hb indicates fetal blood, also alpha- fetoproetin

25. EDTA is the anticoagulant of choice for blood collection for DNA extractions. It inhibits DNAase activity and does not introduce volume changes Sample should be shipped as early as possible within 24 hours. DNA test

26. Wet blood is more significant than dried blood because the forensic scientist can perform more tests to gain insight to the happenings of the crime. Blood begins to dry after 3-5 mins of exposure to air. As it dries, it changes color from deep red to brown and black. Blood can be categorized into pools, drops, smears or crusts. Wet Vs dry blood

27. MURDER Blood on the weapon can be matched against the blood of the victim. Blood stains on clothing or person of the accused can be matched with the victim. Hair roots found on weapon can be matched with that of the victim of the accused ACCIDENTAL DEATHS (RTA etc.) Blood stains on the tyre or other parts of the offending vehicle may give a clue Nature of the crime

28. SEXUAL CRIMES Blood stains on thighs or private parts of the victim PATERNITY DISPUTES HLA, DNA BLOOD OF PREGNANCY/ABORTION Presence of chronic gonadotrophin

29. DEATH DUE TO ASPHYXIA Dark fluid blood in heart chambers DEATH DUE TO DROWNING Alteration in chloride’s content in blood DEATH DUE TO POISONING Cherry pink color in CO poisoning Brick red in Cyanide poisoning CAUSE OF DEATH

30. CATEGORIES OF BLOOD STAINS

31. ARTERIAL BLOOD Copious Bright red in color Spurting VENOUS BLOOD Dark red Oozes out gradually ARTERIAL OR VENOUS BLOOD

32. ANTEMORTEM BLOOD Due to presence of fibrin blood effused during life can be peeled off in scales upon drying. POSTMORTEM BLOOD Blood flowed after death tend to break into powder upon drying. ANTEMORTEM/POSTMORTEM BLOOD

33. Wear protective clothing, gloves, masks and eye protection as the situation warrants. Photographs should be taken from all angles. COLLECTION OF BLOOD STAIN

34. Sodium fluoride EDTA Potassium oxalate Citrate 4 degrees celsius temp