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Trace evidence blood group

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Trace evidence blood group

  1. 1. Trace evidence Blood Group Dr Arman Hossain
  2. 2. Forensic science > Forensic science laboratory : Forensic science > Forensic science laboratory : Forensic science is the study & application of different scientific knowledge to the process of law involving the scientific examination & evaluation of evidences.
  3. 3. Major divisions of Forensic science laboratory 1.Physical & chemical instrument division 2.Biology division 3.Serology division 4.Toxicology division 5.Chemistry division 6.Documents examination division 7.Photography division 8.Lie detection division 9.Museum
  4. 4. Trace evidence Trace evidence : Any trace substance which could be found in the scene of crime with assailant or victim of the crime that has evidential value to link or investigate crime is trace evidence. Ex: Semen, hair, bloodstain
  5. 5. Locard’s Principle of Exchange Locard’s Principle of Exchange (Lawyer & doctor Edmond Locard, 1877-1966): It states that when any two objects come into contact, there is always a transference of material from each other. In other words, when an act of crime is committed there must be sign of crime both in the accused & the victim.
  6. 6. Some important trace evidences Some important trace evidences -Blood stain, seminal stain, hair, Saliva stains, vaginal fluid, fecal stains, vomits stains, urine, skin, tooth pulp, nails & dandruff, nail mark, bite mark etc.
  7. 7. Seminal stain as trace evidence Semen : It is grayish yellow, thick, jelly like alkaline fluid with characteristic order, consists of spermatozoa, epithelial & other cells suspended in a fluid known as seminal plasma. Quantity: 2-5 ml/ejaculation Sperm count: 200-500million/ejaculation. 100million/ml, 200-500 reach to the ampulla, 90% motile at ejaculation.
  8. 8. Circumstances in relation to semen examination 1.Rape or attempted rape 2.Lust murder 3.Unnatural sexual offences 4.Disputed paternity 5.Legitimacy 6.Sterility 7.Divorce case 8.Artificial insemination
  9. 9. Materials may me stained with semen- 1.Clothes 2.On person 3.Bedclothes 4.Seats of a motorcar 4.The floor of grass at the scene of crime.
  10. 10. Collection of materials 1.Dried or drying seminal stain on the perineum or thighs is collected with damp swab. 2.Stain from the vagina is collected with a pipette/throat swab/vaginal washing 3.A portion of fabric containing seminal stain is cut out, dried & preserved. 4.The pubic hair with seminal stain should be plucked & placed in a container. 5.Seminal stain on a smooth & impervious surface should be gently scraped with the point of a knife into a glass container.
  11. 11. Examination of seminal stains 1.Physical 2.Chemical 3.Enzymatic 4.Microscopic
  12. 12. Tests for semen 1.Florence test 2.Barbario’s test 3.Acid phosphatase test 4.Creatine phosphokinase test 5.Ammonium Molybdate test 6.Gel electrophoresis test 7.Test for blood group factors in the semen.
  13. 13. Hair as trace evidence May answer many questions of medico legal importance – 1.Is it hair or not –Cuticle, cortex, medulla 2.Human or animal 3.Male of female 4.From what part of the body 5.Age of the person 6.Identical with that of victim or suspect 7.Naturally forcefully removed 8.Detection of poison 9.Identification of weapon 10.Peculiarity of hair 11.Sexual offence & hair 12.Time since death
  14. 14. Difference between human hair & animal hair Points Human hair Animal hair 1.General character 2.Cuticle 3.Cortex 4.Medulla 5.Pigment 6.Shaft diameter 7.Precipitin test 1.Fine & thin 2.Cuticular scales are soft, thin & flattened 3.Well striated, 4-10 time as broad as medulla 4.Thiner, even may be absent. 5.More towards the periphery of the cortex 6.Usually 50-150µm 7.Specific for human being. 1.Coarse & thick 2.Cuticular scales are very marked with large & step like or wavy projections. 3.Thin, rarely more than twice as broad as medulla. 4.Wider 5.It may be central, peripheral or uniform. 6.Either <25 or>3000 µm. 7.Specific for animal
  15. 15. Blood stains as trace evidence Medico legal importance of blood: Civil: 6.Diputed parenthood 7.Divorce & nullity of marriage 8.Compensation case 9.Medical negligence
  16. 16. Blood stains as trace evidence Criminal 1.Identification of the victim or offender of a crime – homicide, sexual offences etc. 2.The cause of death –detection of poison, pathology 3.Time of death –different chemical & biochemical tests 4.Time of crime/injury 5.Criminal abortion 6.The malingering case
  17. 17. DD of bloodstains 1.Rust stain or mineral stain 2.Vegetable stain –bleached with chlorine water 3.Synthetic dry stain –react with HNO3 4.Stain of grease, tar or pitch –dissolve in alcohol, chloroform, ether
  18. 18. Variety of bloodstains 1.Drop 2.Splashes or exclamation mark 3.Pools 4.Spurts or squirt 5.Smear 6.Trails
  19. 19. Questions of MLI in relation to blood & blood stain 1.Blood or not 2.Human blood or animal blood 3.Source of blood –single/multiple, victim/assailant, arterial/venous/menstrual/vomited/haemoptysis/abortus/pat hologial 4.Antemortem or postmortem 5.Time of death 5.Age of the person 6.Sex of the person 7.Blood group of the person 7.Time of bleeding 8.DNA profiling
  20. 20. Examination of blood/blood stains 1.Physical examination 2.Microscopic examination 3.Spectroscopic examination 4.Chemical examination 5.Sero-immunological tests
  21. 21. Tests for of blood/blood stains 1.Spectroscopic examination detects –Oxyhaemoglobin, reduced haemoglobin, carboxy-haemoglobin, methaemoglobin, acid hemin, haemocromogen 2. Chemical tests – A.Benzedine test B.Phenophthalin test (Kastle Meyer test) C.Leucomalachite green test D.Orthotolidine test (Khon & O’kelly test) E.Luminal test
  22. 22. Tests for of blood/blood stains 3.Microchemical tests/Crystal tests/Tests for haemoglobin of blood (Confirmatory tests) A.Haemocromogen crystal test (Takayama test) B.Haemin crystal test (Teichmann’s test) 4.Sero-immunological tests A.Ring test B.Antiglobulin consumption test C.Mixed antiglobulin test D.Diffusion precipitaion in gel E.Passive haemagglutination test F.Gel electrophoresis test G.Precipitin test
  23. 23. Difference between ante mortem and post mortem clot Point Ante mortem clot Post mortem clot 1.Consistency More firm & friable. Rubbery & gelatinous. 2.Composition Composed of mainly of platelets & fibrin or aggregated platelet producing fibrin strands entangling the blood cells. Lack of fibrin strands. 3.Attachment to the underlying vessel wall Almost always has a point of attachment. Lacks attachment to the underlying vessel wall. 4.Lines of Zahn May be present Absent 5.Dryness Dry Moist 6.Site of formation In the living circulation Clotting after death and also in extravascular accumulations of blood.
  24. 24. Difference between fresh & menstrual blood Point Fresh blood Menstrual blood 1. Clot formation Occurs Not occurs 2.Colour Bright red Dark red 3.Odour Salty odour Fishy odour 4.Viscosity Less viscid More viscid 5.Reaction Alkaline Acidic 6.Presence of endometrial and vaginal epithelial cell Absent Present 7.Presence of micro organism Absent (except disease) Lactobacilli, Trichomonas vaginalis, Candida albicans etc are present.
  25. 25. Difference between male & female blood Traits Male blood Female blood 1. Sex chromatin in leukocytes 44+XY 44+XX 2. Davidson’s body in neutrophil Absent Present in upto 69% neutrophils of females
  26. 26. Blood group • Red cell membranes have antigens on their external surfaces • These antigens are – unique to the individual – recognized as foreign if transfused into another individual – promote agglutination of red cells if combine with antibody – more than 30 such antigen systems discovered • Presence or absence of these antigens is used to classify blood groups • Major blood groups – ABO & Rh • Minor blood groups – Kell, Kidd, Duffy etc
  27. 27. Genotype & Phenotype ABO system AA –A BB –B OO –O AB –AB MN System MM –M NN –N MN –MN Rh Factors Rh+ve Rh-ve Antigens –Cc,Dd, Ee.
  28. 28. ABO Blood Groups • Most well known & clinically important blood group system. • Discovered by Karl Landsteiner in 1900 • It was the first to be identified and is the most significant for transfusion practice • ABO blood group consist of o two antigens (A & B) on the surface of the RBCs o two antibodies in the plasma (anti-A & anti-B)
  29. 29. Reciprocal relationship between ABO antigens and antibodies
  30. 30. ABO antigens & corresponding antibodies
  31. 31. Inheritance of ABO Blood Groups • Follows Mendelian principles • Blood group antigens are “codominant”- if the gene is inherited, it will be expressed. • There are three allelic genes -A, B & O • Some aberrant genotypes do occur but they are very rare. • Understanding of basic inheritance important.
  32. 32. Inheritance of ABO Blood Groups • Two genes inherited, one from each parent. • Individual who is A or B may be homozygous or heterozygous for the antigen. o Heterozygous: AO or BO o Homozygous: AA or BB • Phenotype is the actual expression of the genotype, ie, group A • Genotype are the actual inherited genes which can only be determined by family studies, ie, AO.
  33. 33. Example of Determining Genotype • Mother’s phenotype is group A, genotype AO • Father’s phenotype is group B, genotype BO
  34. 34. Other Examples
  35. 35. Rh typing • Normal typing for Rh antigens only includes typing for Rh (D). • The result of this typing determines the Rh status of the cells (Rh - positive or Rh - negative). • Some Rh typing sera is diluted in high protein solutions and may require a negative control. • It is recommended to use two monoclonal anti-D sera from two different manufacturers labeled as D1 and D2, especially to confirm all Rh negatives
  36. 36. Various antigens in Rh system
  37. 37. Rh+ve & Rh-ve blood type Genotype Blood type (+,-) or (+,+) Rh+ (-,-) Rh-
  38. 38. Importance of blood grouping 1.Disputed paternity 2.Disputed maternity 3.Source of blood 4.Stains due to body fluid 5.Identity 6.Cause of death 7.Miscarriage 8.Assist in matching in disaeter.
  39. 39. Thanks to all
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Trace evidence blood group


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