BLOODSTAIN PATTERNS

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BLOODSTAIN PATTERNS. BLOOD COMPONENTS. Plasma fluid portion of normal unclotted blood red blood cells, white blood cells, and platelets are suspended in it. BLOOD COMPONENTS. Serum liquid portion of clotted blood. SURFACE TENSION OF BLOOD. - PowerPoint PPT Presentation

Transcript of BLOODSTAIN PATTERNS

Bloodstain Patterns

BLOODSTAIN PATTERNSBLOOD COMPONENTSPlasmafluid portion of normal unclotted blood red blood cells, white blood cells, and platelets are suspended in it

BLOOD COMPONENTSSerumliquid portion of clotted blood

SURFACE TENSION OF BLOODheld together by strong cohesive molecular forcesouter skinSurface tension lightly less that that of waterLiquid mercury is about 10x greater Blood does not fall in teardrop configurationSURFACE TENSIONTo create splatters, an external force must overcome surface tension of bloodSURFACE TENSIONSurfacesGenerally, clean glass or smooth tile, very little splatterRough texture, wood or concrete, significant splatterGEOMETRY OF BLOODSTAINCan determine direction of flight by examining edge characteristicsGEOMETRYAngle of impact 90 degrees results in circular shape

GEOMETRYAngle of impact Less than 90 degrees Elongated

GEOMETRYIf you measure width & length of an elliptical bloodstain you can calculate angle of impactDivide width by length take sin-1 gives angle of impactGeometryOnce get angle of impact for each bloodstain3D origin may be determined

DIRECTION OF TRAVELNarrow end of elongated blood stain points in direction of travel

SPATTERED BLOODrandom distribution of bloodstains that vary in size that may be produced buy a variety of mechanismsSPATTERED BLOODExamples:GunshotBeatingStabbingpower toolsArterialcast-offpassiveSPATTERED BLOODmay allow determination of an area or location of origin of blood sourceSPATTERED BLOODIf found on a suspects clothing, it may place that person at scene of violent altercationSPATTERED BLOODMay allow determination of mechanism by which pattern was createdSIZE, QUANTITY AND DISTRIBUTION OF SPATTER DEPENDS ONQuantity of blood subjected to impactForce of impactTexture of surface impacted by bloodGUNSHOTHigh Velocity SpatterMisting effectVarying sizes of impact spattersDepend of caliber of weapon, location, number of shots, etc.Gunshot

EXAMPLE BACK SPATTER

EXAMPLE GUNSHOT IMPACT SPATTER

Beating and Stabbing Impact SpatterMedium Velocity SpatterGenerally size range 1-3 mm in diameter

Castoff Bloodstain PatternsLow Velocity SpatterBlood flung from object such as bat or knife

Passive BloodstainsLow VelocityBlood dripping from injured person

What happens when blood hits blood?Drip patterns

Large Volume BloodstainsSplashing and ricochetOften from victim with large wound or vomitingEXPIRATED BLOODSTAIN PATTERNSBlood accumulates in lungs, sinuses, airway passages of victimForcefully expelled from living victimCan look similar to other bloodstain patternscan only be explained if victim has blood on faceARTERIAL BLOODSTAIN PATTERNSCan be very large gushing or spurting patterns to very small spray types

OTHER BLOODSTAIN PATTERNSTransfer bloodstain patternsAltered bloodstainsVoid areas or patterns

INTERPRETATION OF BLOODSTAINS ON CLOTHING AND FOOTWEARWhose blood is it?How did it get there?LUMINOLUsed for latent bloodstains at crime scene

CHALLENGESBloodstain pattern interpretation can be very complexNeed solid grasps of:MathematicsPhysicsscientific methodpractical experience