Presentation on theme: "Serology Blood Spatter Analysis The Makeup of Blood 1/12 of the body is blood. Liquid portion of blood Blood is suspended in a liquid called plasma."— Presentation transcript:
The Makeup of Blood 1/12 of the body is blood. Liquid portion of blood Blood is suspended in a liquid called plasma (makes up 55% of blood). Composed of 90% water and 10% metabolites and waste, salts and ions (Na+, Cl-, HCO3-). Solid Portion of Blood Erythrocytes: red blood cells. Contains hemoglobin; carries O2 from lungs to cells and then CO2 back to lungs. Leukocytes: White blood cells. Primary cells for immunity; produce antibodies. Platelets: create clots by initiating the formation of fibrin. If the clot is removed a pale-yellow, watery fluid is present known as serum.
Other Blood Components Hemoglobin: Oxygen carrier that gives red blood cells their color. Composed of four globin (protein) chains, each with a heme group.
Other Blood Components Antibodies: proteins in the blood or secretory fluids that tag, destroy or neutralize bacteria, viruses, or other harmful toxins, producing an immune response. Antigens: foreign substances in the body that are capable of causing disease. The presence of antigens triggers an immune response, usually the production of antibodies. Antiserum: human or animal serum containing antibodies that are specific for one or more antigens.
Blood Reaction: Serum and Agglutination Serum: a liquid that separates from clotted blood. Agglutinations: A type of allergic reaction where red blood cells clump together, usually in response to a particular antibody.
ABO Characterization (Used for Blood Typing) Inexpensive and easy to perform compared to DNA testing. 80% of populations is a secretor (person who’s blood type antigens are found in other body fluids).
ABO Characterization - Antigens Characteristic chemical structures found on the surface of RBCs. There are two antigens for the ABO system; A & B. Antigens – A RBC have A antigens – B RBC have B antigens – AB RBC have both A & B antigens – O RBC have neither.
ABO Characterization - Antibodies Protein manufactured by WBCs which are found in serum. Produced to attack invaders (antigens) that enter the bloodstream. This is the basis for vaccines. If Type A receives blood from type B, antibodies will form to destroy the B antigen. This is done through agglutination (clumping).
ABO Characterization Donor vs. Recipient If the wrong blood is given it could be fatal.
Rh Factor Sometimes referred to as the D antigen. Carriers are Rh+ (85% of population) Noncarriers are Rh-
Serology – Blood Typing Improtant for Forensic Science Used to show the probability of two sample having different origins. Used to exclude suspects. Blood TypePercentage Type A40% Type B11% Type AB4% Type O45% Rh+85% Rh-15%
Serology – Blood Typing Probability Equation: What is the probability of a person having type B+ blood? – 11 x 85 = 935 or about 1 out of 10 people 100 100 10,000 – Give the probability of a person having type AB- blood.
Serology – Blood Typing For unknown blood to be “typed” a drop of blood is added to serum containing known antibodies. Whether there is agglutination determines the blood type in the ABO system.
Blood at the Crime Scene Class evidence: A transfer of blood between victim and suspect or crime scene. ◦ Blood typing (A, B, AB, O). Can become individualized by comparing DNA with proper conditions, time and equipment. Courtesy of NYPD
Detection of Blood If a substance is discovered at a crime scene that looks like blood, it must first be tested to determine if it is in fact blood. You will then need to determine if the blood is from human or other animal origin. Presumptive test: screening tests to determine the presence of the substance but are not confirmatory.
Presumptive Tests - Chemical Hematest tablets and Hemastix strips: – The heme in hemoglobin catalytically breaks down peroxides with the production of oxygen. Oxygen reacts with the benzidine product in the Hematest tablet/Hemastix to turn it blue. – False positives: dry bleach residues and some plastics.
Presumptive Test - Chemical Kastle-Meyer test: ◦ Basted on the catalytic breakdown of peroxides by hemoglobin. Contact of reduced phenolphthalein reagent and hydrogen peroxide with a bloodstain produces a deep pink color. ◦ False positives: potatoes and horseradish.
Presemptive Test - Chemical Luminol Test: ◦ Very sensitive. Can detect dried and even washed out blood. Makes old blood stains chemiluminesce/glow (emission of light from a chemical reaction). ◦ Chemiluminescence reaction ◦ A + B [I]* products + light [I]* is an excited state ◦ False positives: metals (Cu, Fe, Co), bleach, and sometimes plaster walls.
Human vs. Animal Once the stain has been determined as blood, it must then be determined if the blood is from human or other animal origin. Precipitin test: standard method of testing. Extremely sensitive. Used on very diluted or very old blood. – Uses an animal serum that contains antibodies specific to human antigens. This causes agglutination with human blood.
How it Works – Precipitin Test A rabbit is injected with human blood. Antibodies are produced to fight the foreign invader. The rabbit serum containing these antibodies is used in the precipitin test. This results in agglutinations. This is similar to a chemical precipitation.
Serology The laboratory study of body fluids using specific antigen and serum antibody reactions. Karl Landsteiner – Father of Serology – 1901 Worked out the ABO blood typing system. – 1940 he discovered the rhesus factor (Rh) in blood.
Blood Spatter Analysis The way in which blood falls, smears, projects and its directionality can help recreate the crime. Also used to prove or disprove the suspects account of what happened.
Blood Spatter Analysis Words to Know Angle of impact Arterial spurting pattern Back spatter Blood spatter analysis Bloodstain Cast-off pattern Contact stain Direction of flight Directionality Directionality angle Draw-back effect Drip pattern Expirated blood Flight path Flow pattern Forward spatter High-velocity impact spatter Impact pattern
Blood Spatter Analysis Words to Know Impact site Low-velocity impact spatter Misting Parent drop Passive drop (bleeding) Point (area) of convergence Point (area) of origin Projected blood pattern Satellite spatter Spatter Spine Swipe pattern Target Transfer or contact pattern Void Wipe pattern
Bloodstain Evidence May reveal: Origin(s) of bloodstain Distance of bloodstain from target Direction from which blood impacted Speed with which blood left its source Position of victim & assailant Movement of victim & assailant Number of blows/shots 1
Liquid Blood Physical properties – viscosity – surface tension – specific gravity Behaves as a projectile in motion – biology, physics, maths 2
Surface Tension Resistance to penetration & separation Surface acts to reduce surface area Smallest SA (surface area) to Volume ratio is offered by sphere 3
Dripping Blood Blood drop grows until Wt (G) > Surface tension Single drop breaks free (teardrop shape) Surface tension pulls in vertically Shape settles into sphere (0.05 ml) Does not break up until impact And horizontally Blood trickles downwards 4
Drop size. Standard drop size 50ul (0.05ml). Rapid bleeding gives slightly larger drop Shaking/movement casts off smaller drops. 5
Free Falling Blood Droplets. 50 ul 4.6 mm 7.5 m/s 4.2 to 5.4 m 0.5 ul 2.12 mm 2.4 to 3 m. 4.6 m/s 0.12 ul 1.32 mm 0.84 to 1 m. 3.3 m/s 0.06 ul 1.1 mm 0.5 to 0.65 m. 2.2 m/s 8
Shape & Size of Bloodspot Depends mostly on nature of target surface – texture (rough or smooth) – porous or non porous Size is related to distance fallen, provided: – standard 50 ul drop of blood There is little change in spot diameter beyond a fall distance of 1.2 m 9
Height Fallen Single drops of blood falling from fingertip onto smooth cardboard from various heights. No change in diameter beyond 7 ft. Adapted from Introduction to Forensic Sciences, W. Eckert, CRC, 1997 10
Effect of Target Surface...... Spreads out smoothlyST of spreading edge is broken by irregular surface 11
Experiments with Falling Blood Droplets blood dropper ruler Terazzo floor whiteboard rough paper towel paper Fabric (theatre green) Height Target Surface 12
Height/Surface Single drop of blood falling from various heights (m) onto various surfaces smoothfloorpapertowelfabric 0.5 1 2 3 1 2 3 13
Angle of Impact 90 10 70 20 30 60 50 40 Adapted from Introduction to Forensic Sciences, W. Eckert, CRC, 1997 80 Gravitational dense zone at lower edge 14
Wave Cast-off David Sadler:. Parent drop wave cast-off Tail of wave cast-off points back to parent drop Tail of elongated stain points in direction of travel 15
Point of Convergence 5 ml blood squirted from a syringe from height of 1 m 17
Point of Origin length width Angle of impact = arc sin W/L Distance from point of convergence Height above point of convergence Origin 85 60 45 30 181
Tracing Origin of Bloodspots Point of convergence method – 2 dimensional image Point of origin method –adds 3rd dimension to image In practice: –use of string & protractor at scene –use of computer at laboratory 19
Blood Spatter Low velocity (5 f/s, 1.5 m/s) – e.g. free-falling drops, cast off from weapon Medium velocity (25 - 100 f/s, 7.5 - 30 m/s) – e.g. baseball bat blows High velocity (>100 f/s, 30 m/s) – e.g. gunshot, machinery 20
Low Velocity Blood Spatter Blood source subjected to LV impact – < 5 f/s (1.5 m/s) Spot diameter: mostly 4 - 8 mm – some smaller, some larger Free-falling drops (gravity only) Cast off from fist, shoe, weapon Dripping Splashing Arterial spurting 22
Cast-off from Weapon First blow causes bleeding Subsequent blows contaminate weapon with blood Blood is cast-off tangientially to arc of upswing or backswing Pattern & intensity depends on: – type of weapon – amount of blood adhering to weapon – length of arc 23
Medium Velocity Blood Spatter Blood source subjected to MV impact – (25 - 100 f/s, 7.5 - 30 m/s) Spot diameter: mostly 1 - 4 mm Blows with weapon (e.g. baseball bat) 54
Medium velocity blood spatter. Point of impact 15 cm in front of vertical target surface 6” ruler 55
High Velocity Blood Spatter Blood source subjected to HV impact – > 100 f/s, 30 m/s Fine mist: spot size < 0.1 mm Small mass limits spread to 1 m !Some larger droplets reach further Gunshot – back-spatter from entry wound – forward spatter from exit wound High speed machinery 58
Gunshot: back& forward spatter Bloodstained foam held just above target surface. Back-spatter on entry Forward spatter on exit bullet Bullet passing L to R just above sheet Bullet enters foam bullet exits foam 59
Gunshot Back Spatter Arises from entrance wound Passes back towards weapon & shooter Seen only at close range of fire Seen on: – inside of barrel – exterior of weapon – hand, arm, chest of shooter 60
Forward spatter (5 ms after bullet impacted at 1000 f/s) 2.5 cm blood soaked target bullet 63
Gunshot Forward Spatter Arises from exit wound Passes forwards in same direction as shot More copious than back-spatter Can be seen at any range of fire Seen on nearby surfaces, objects, persons – especially on wall behind victim 62
Case Study Sam Sheppard Early on the morning of July 4 th, police received a call from Dr. Sam Sheppard. He reported that his wife, Marilyn, was dead in their bedroom. He explained to police that, the night before, Marilyn had left him on the couch and gone to sleep in the twin bed next to Sam’s. He fell asleep and awoke sometime later, believing he heard his wife calling his name. Going upstairs, he saw Marilyn covered with blood. He checked for her pulse and found none.
Sam Sheppard cont’d Sheppard heard a noise below, ran downstairs, and saw someoe moving toward the lake. He chased the person across the lawn and down the steps leading to the beach. He struggled with a man 6’3”, middle-aged, with dark bushy hair and a white shirt. Sheppard was choked to unconsciousness. Marilyn had 35 wounds to the head, and blood drenched the walls, door, and bed where she lay. Her face was almost unrecognizable.
Sam Sheppard Case Look at the crime scene photos. Do you believe Sheppard’s story or is he guilty of his wife’s murder?
Sam Sheppard Case Sheppard served 10 years in prison before the U.S. Supreme Court ruled tat his trial had been tainted. The evidence was reexamined; blood spatters in the bedroom and blood drops throughout the house gave some of the most telling evidence. The expert, Dr. Paul Kirk, concluded that the killer could not have been Sam because the killer was left handed. Dr. Sheppard was right-handed. - FSHS