Forensic Science: Blood Types PDF

FORENSIC SCIENCE BLOOD: Forensic serology Explain blood biochemistry in terms of blood type explain how to analyse suspected blood stains explain how to interpret blood spatter patterns Blood on the Suspect Is it blood? How can we see invisible Is it human blood?...

FORENSIC SCIENCE BLOOD: Forensic serology Explain blood biochemistry in terms of blood type explain how to analyse suspected blood stains explain how to interpret blood spatter patterns Blood on the Suspect Is it blood? How can we see invisible Is it human blood? Hains? Whose blood is it? In a violent crime, blood will be scattered around the crime scene. Can the pattern of blood spatter be used to reconstruct the events? Blood Composition Blood – about 8% of body weight Blood Plasma – the fluid portion of the blood (55% by weight) mostly water, proteins, waste products of metabolism, nutrients on the way to the cells blood is used to transport all sorts of molecules aroundi body Blood Cells – many different types (45% by weight) – Red Blood Cells or Erythrocytes principally for Oxygen transport – White Blood Cells – Lymphocytes, phagocytes etc responsible for the immune response – Platelets for blood clotting Serum – the liquid that separates from blood when a clot is formed. Erythrocytes Principle function Oxygen transport on the Haemoglobin protein - 4 Fe atoms in 1Hb 4 oxygen molecules on each protein & bind to atoms duringOn transpis Fe Large quantities of carbonic anhydrase catalyse the reaction of CO2 to HCO3- for the soluble - Approximately 7.8 microns in transport of CO2 in the blood to lungs for removal diameter (5 million/L) Biconcave structure No nucleus Blood Typing Surface of the red blood cells contains proteins called Antigens There are 30 commonly occurring antigens with >100 rarer ones identified The most common antigens A-B-O system of blood typing Karl Landsteiner (Nobel prize 1930) ABO Blood Types Four basic Blood Types Type A – A Antigen on the cell surface Type B – B Antigen on the cell surface Type AB – both A and B antigens Type O - neither A or B antigens Occurrence in the population (Singapore) O 40% A 25% B 30% AB 5% occurrence of BT vary from country to country & from racial to racial grp gup Blood Types (answer: No) “I am type B and have the tendency to be simplistic and straightforward at times” Ryu Matsumoto  blood ~ floating I in Antibodies Constitute about 20% of the blood plasma volume sites 2 antigen binding Class of proteins called “Immunoglobins” Produced by plasma cells as part of the immune response Bind to objects in the blood that they recognise as “alien” Y-shape Serum Antibodies The blood serum contains antibodies to the surface antigens Anti-A, Anti-B The antigen-antibody interaction is highly specific ~ Anti-A antibody will only A antigen etc Basis of the immune response recognise. , Agglutination Mixing Blood Type A with Type B allows the Anti-A (from B) to mix with A antigen Type A causes agglutination Results in Blood Clotting Blood transfusion has to match the blood type Agglutination anti-B does not recognise type A – no agglutination anti-B recognises type B, causing This is the situation in a agglutination person with blood group A - what would happen if a type A person were given type B blood in a transfusion > agglutinate -  using more antigens Blood Type Distribution (Singapore) can get more highly individualised system Blood Group Rhesus Antigens: O+ 34% D antigen is most prevalent O- 6% Rhesus – Positive with D antigen Rhesus – Negative without D antigen A+ 21% A- 4% 85 % of people are Rh+ B+ 25.5% 15% are Rh- B- 4.5% AB+ 4% AB- 1% (50,000) Yeast common BT Gill Not highly individualised Bio-Identification ABO  is not a unique way identification More complex blood typing such as: O Rh negative: D- C-E-c+e+, M+S-, Le(a-), K-, Fy(a+b-), Jk(a+b-) CMV- Reduces the probability Extensive Research prior to 1990 Inferior to DNA fingerprinting I individualised more highly Blood type cannot prove guilt – not individualised Blood type can establish innocence Is it blood? Presumptive Tests for Blood ~ no longer used be of toxicity Benzidine Colour Test of benzidine Kastle-Meyer Colour Test uses Phenolphthalein Luminol Test Based on the peroxidase properties of blood H2O2 H2O + O -not free O atom 1 " blood will catalyse e breakdown of Hron to He Luminol Test after this test blood , I is still in suitable a cord? Method used at the crime scene to do part analysis Sensitivity 30 parts per million blood will this catalyse + Y & form in an excited state it will drop back down to state ground & : every diffe will be given of in form of electromagnetic radiat, in this case of 3-aminophthalate , & excited State At betw ground corresponds to blue light  Chemical basis of the Kastle-Meyer Test Swab the sample Add reduced Phenolphthalein to swab Add H2O2 to the swab oxidisinis blood will catalyse e by Hro2 to Lused for e I pink colour give test Anything that can catalyse the oxidation will give a “positive”, even a potato “false positive” Kastle-Meyer Test possible Blood Stain Positive Kastle-Meyer test  Precipitin Tests based on anti-sera produced in rabbits or rats Inject human blood into a rabbit –the rabbit produces antibodies to human blood. Human anti-sera are available commercially. Other animal anti-sera are available to eliminate pets at the crime scene antibodies will bind ecomponents of that contains human blood - antibodies giving precipitin Precipitin Lif there is an interacti , if no interacti , it is not a human blood after all  Why do we want to know about animal blood? 2004: Christopher Nudds (left) accused of killing Fred Moss (right). Many blood stains in Nudds’ Range Rover - but he is a hunter Most: birds and rabbits Human blood stains: DNA match to Fred Moss Precipitin Test Is it blood? which species? luminol or precipitin test Kastle-Meyer test blood type DNA grouped, but not individualised individualised Blood Patterns Blood on the Suspect In a violent crime, blood will be scattered around the crime scene. Can the pattern of blood spatter be used to reconstruct the events? Blood spatter shoe print hand print trsf of blood someone stepped in a pool of from hand to wall blood , got blood on their shoe, transfer of blood Blood Spatter Analysis artery blood drip onto blood – when is happens ~ severed areunder arteries eure spurting when exact pattern depends on , arterial surface I are severed , I blood spurts splash pattern they blood hitI wall & out i some velocity a. as pressure dribbled downwards artery in is due to I beatingf : heart , you get a pressure surge everytime e heart beats , so you may get multiple patterns close tgt due to multiple heartbeats each cangy an arterial splurt Blood spatter low velocity spatter Medium velocity spatter and cast-off 1.5 m/s e.g. baseball bat Free fall and cast off Up to 30m/s much greaerred High velocity e.g. gun shot more finer droplets Blood spatter A falling blood drop is spherical and will give a circular mark on the floor if falling at 90º to surface e (falling vertically) Blood spatter If the blood drop hits the wall or floor at an angle, the width and length of the mark will be different. The angle can be calculated by comparing the width and length. there can be a little bit of splash shape of blood droplets depend4 on second main mark remark blood came a in shallow 4 of very LHS Blood Droplet Patterns very elongated shape perfectly - circular Blood Spatter Analysis If we know the angle at e where event happened which the blood drop hit - the wall or floor, we can project back. Where the lines all cross (convergence point), was the source of the blood. if there are multiple blood spatters , can plot I trajectory e of blood droplets backwards ed if i blood drops care fromsingle a event , e. g. single gunshot single impact , but all converge to i a they , hd a single point called convergence pt. Blood Spatter Patterns 30 you can gete distance betw 2 walls & i height above e floor determine posit: of victim , e q.. victim was standing/ i on floor when e impart happened Blood spatter sometimes it can be too confusing & interpretat is not possible Lord Lucan Banker turned professional gambler Deeply in debt Separated from Lady Lucan This wife  London, November 7th, 1974 9.45 pm Lady Lucan runs into pub Bloodstained “help me, help me, help me, I have just escaped from being murdered” At her home, the nanny is dead; children upstairs asleep The crime scene 4 upper floors Ground floor Bent, bloodstained lead pipe in the hallway Blood stains at top of stairs that lead toe basement Door to basement is open Breakfast room: blood on walls and floor Pool of blood - man’s footprint Blood stained sack containing nanny’s body 11.30 pm Lord Lucan visits a friend 60 km outside London, posts letters, leaves; Car found at Newhaven (by the sea) three days later His story Walking past the house, saw a struggle in the basement, went in to help Lady Lucan, man runs off, he cannot follow because he slips in the pool of blood. After Lady Lucan runs out of the house, he flees because he thinks that he will be blamed Her Story 8.30 Nanny puts the children to bed Note: same height and weight as Lady Lucan Should have been her night off 8.40 Nanny goes to basement to make tea 9.15 Lady Lucan goes to look for her; attacked by her husband in the hallway; stop fighting; she escapes to the pub Blood Blood groups ~ ground floor Lady Lucan A Top of stairs: A Nanny B Basement: B Lead pipe: A and B Where was Lady Lucan attacked? Did Lord Lucan slip or step in the blood? There have been no confirmed sightings of Lord Lucan since that night. Now legally presumed to be dead. Blood Is it blood? Kastle-Meyer and luminol tests Is it human blood? Precipitin Whose blood is it? Blood typing – but not individualised How did it get there? Blood Spatter Analysis