2 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
3 Detection of BloodIf 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.
4 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.
5 HemoglobinOxygen carrier that gives red blood cells their color. Composed of four globin (protein) chains, each with a heme group.
6 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.
7 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 reactionA + B [I]* products + light[I]* is an excited stateFalse positives: metals (Cu, Fe, Co), bleach, and sometimes plaster walls.
8 Human vs. AnimalOnce 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.
9 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.
10 Antibodies, Antigens and Antiserum 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.
11 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.
13 SerologyThe laboratory study of body fluids using specific antigen and serum antibody reactions.Karl Landsteiner – Father of Serology1901 Worked out the ABO blood typing system.1940 he discovered the rhesus factor (Rh) in blood.
14 Serology - Blood The make up of blood. 1/12 of the body is blood. Blood is suspended in aliquid called plasma (makesup 55% of blood).Composed of 90% water and10% metabolites and waste,salts and ions (Na+, Cl-, HCO3-).Solid portion of bloodErythrocytes: 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.
15 Serology - ABO Characterization 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).
16 Serology – ABO Characterization Antigens Millions of characteristic chemical structures are found on the surface of RBCs.There are two antigens for the ABO system; A&B.AntigensA RBC have A antigensB RBC have B antigensAB RBC have both A & B antigensO RBC have neither.
18 Serology – 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.
20 Serology – ABO Characterization Donor vs. Recipient If the wrong blood is given it could be fatal.
21 Serology – Rh Factor Sometimes referred to as the D antigen. Carriers are Rh+ (85% of population)Noncarriers are Rh-
22 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.
23 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.
24 Blood Spatter Analysis Words to Know Angle of impactArterial spurting patternBack spatterBlood spatter analysisBloodstainCast-off patternContact stainDirection of flightDirectionalityDirectionality angleDraw-back effectDrip patternExpirated bloodFlight pathFlow patternForward spatterHigh-velocity impact spatterImpact pattern
25 Blood Spatter Analysis Words to Know Impact siteLow-velocity impact spatterMistingParent dropPassive drop (bleeding)Point (area) of convergencePoint (area) of originProjected blood patternSatellite spatterSpatterSpineSwipe patternTargetTransfer or contact patternVoidWipe pattern
26 Bloodstain Evidence May reveal: 1Bloodstain Evidence May reveal:Origin(s) of bloodstainDistance of bloodstain from targetDirection from which blood impactedSpeed with which blood left its sourcePosition of victim & assailantMovement of victim & assailantNumber of blows/shots
27 Liquid Blood Physical properties Behaves as a projectile in motion 2Liquid BloodPhysical propertiesviscositysurface tensionspecific gravityBehaves as a projectile in motionbiology, physics, maths
28 Surface Tension Resistance to penetration & separation 3Surface TensionResistance to penetration & separationSurface acts to reduce surface areaSmallest SA (surface area) to Volume ratio is offered by sphere
29 Dripping Blood 4 Blood trickles downwards Blood drop grows until Wt (G) > Surface tensionSingle drop breaks free (teardrop shape)Surface tension pulls in verticallyAnd horizontallyShape settles into sphere (0.05 ml)Does not break up until impact
30 . . . Drop size 5 Standard drop size 50ul (0.05ml) Rapid bleeding givesslightly larger dropShaking/movementcasts off smaller drops...
32 Shape & Size of Bloodspot 9Shape & Size of BloodspotDepends mostly on nature of target surfacetexture (rough or smooth)porous or non porousSize is related to distance fallen, provided:standard 50 ul drop of bloodThere is little change in spot diameter beyond a fall distance of 1.2 m
33 Height Fallen10Single drops of blood falling from fingertip onto smooth cardboard from various heights.No change in diameter beyond 7 ft.Adapted fromIntroduction to Forensic Sciences,W. Eckert, CRC, 1997
34 Effect of Target Surface 11Effect of Target Surface...Spreads out smoothlyST of spreading edge isbroken by irregular surface
35 Experiments with Falling Blood Droplets 12blooddropperrulerHeightTarget SurfaceFabric (theatre green)rough paper towelpaperwhiteboardTerazzo floor
36 Single drop of blood falling from various heights (m) onto various surfaces 130.51230.5123Height/Surfacesmoothfloorpapertowelfabric
40 Point of Convergence 17 5 ml blood squirted from a syringe from height of 1 mPoint of Convergence
41 Point of Origin Angle of impact = arc sin W/L 85 60 45 30 1 18 Distance from point of convergenceHeight above point of convergenceOriginlengthwidthAngle of impact = arc sin W/L85604530
42 Tracing Origin of Bloodspots 19Tracing Origin of BloodspotsPoint of convergence method2 dimensional imagePoint of origin methodadds 3rd dimension to imageIn practice:use of string & protractor at sceneuse of computer at laboratory
44 Low Velocity Blood Spatter 22Low Velocity Blood SpatterBlood source subjected to LV impact< 5 f/s (1.5 m/s)Spot diameter: mostly mmsome smaller, some largerFree-falling drops (gravity only)Cast off from fist, shoe, weaponDrippingSplashingArterial spurting
45 Cast-off from Weapon First blow causes bleeding 23Cast-off from WeaponFirst blow causes bleedingSubsequent blows contaminate weapon with bloodBlood is cast-off tangientially to arc of upswing or backswingPattern & intensity depends on:type of weaponamount of blood adhering to weaponlength of arc
69 Medium Velocity Blood Spatter 54Medium Velocity Blood SpatterBlood source subjected to MV impact( f/s, m/s)Spot diameter: mostly mmBlows with weapon (e.g. baseball bat)
70 55Medium velocity blood spatter. Point of impact 15 cm in front of vertical target surface6” ruler
71 High Velocity Blood Spatter 58High Velocity Blood SpatterBlood source subjected to HV impact> 100 f/s, 30 m/sFine mist: spot size < 0.1 mmSmall mass limits spread to 1 m!Some larger droplets reach furtherGunshotback-spatter from entry woundforward spatter from exit woundHigh speed machinery
72 Gunshot: back& forward spatter 59Bloodstained foam held just above target surface.Bullet passing L to R just above sheetbullet exits foamBullet entersfoambulletBack-spatteron entryForward spatteron exit
73 Gunshot Back Spatter Arises from entrance wound 60Arises from entrance woundPasses back towards weapon & shooterSeen only at close range of fireSeen on:inside of barrelexterior of weaponhand, arm, chest of shooter
74 Back spatter on steadying hand 61Back spatter on steadying hand
75 Forward spatter (5 ms after bullet impacted at 1000 f/s) 63bulletblood soakedtarget2.5 cm
76 Gunshot Forward Spatter 62Gunshot Forward SpatterArises from exit woundPasses forwards in same direction as shotMore copious than back-spatterCan be seen at any range of fireSeen on nearby surfaces, objects, personsespecially on wall behind victim
90 Case Study Sam Sheppard Early on the morning of July 4th, 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.
91 Sam Sheppard cont’dSheppard heard a noise below, ran downstairs, and saw someone 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.
92 Sam Sheppard Case Look at the crime scene photos. Do you believe Sheppard’s story or is he guilty of his wife’s murder?
93 Sam Sheppard CaseSheppard served 10 years in prison before the U.S. Supreme Court ruled that 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. Video - FSHS
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