Blood Spatter & Crime Scenes

Blood Spatter & Crime ScenesCatalyst: What do you think happened at this crime scene?

Todays AgendaReview of principles from Blood Spatter Height LabDifferent Blood Spatter PatternsPrep for the Fling Lab tomorrow (Last 15 minutes.. regardless of how far we get in the notes.)

Blood Spatter & Crime ScenesThe following notes are long, extensive, and gruesome. To get the MOST out of todays lecture, do not copy everything you see. For each scenario, make sure you have the following information: (1) relative size of blood, (2) relative shape of blood, (3) possible cause of pattern, (4) any other interesting & relevant information.

Dripping Blood

Blood drop grows until Wt (G) > S.T.Single drop breaks free (teardrop shape)Surface tension pulls in verticallyShape settles into sphere (0.05 ml) Does not break up until impactAnd horizontallyBlood trickles downwards4

Drop size.Standard drop size 50ul (0.05ml).Rapid bleeding gives slightly larger dropShaking/movementcasts off smaller drops.5

Free Falling Blood Droplets8

Shape & Size of Bloodspot

Depends 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

9

Height FallenSingle 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 surface11

Wave Cast-offDavid Sadler:

15

Point of Convergence16

Point of Convergence

5 ml blood squirted from a syringe from height of 1 m17

Point of OriginlengthwidthAngle of impact = arc sin W/L181

Tracing Origin of BloodspotsPoint of convergence method2 dimensional image

Point of origin methodadds 3rd dimension to imageIn practice:use of string & protractor at sceneuse of computer at laboratory

19

Blood Spatter

Low velocity (5 f/s, 1.5 m/s)

Medium velocity (25 - 100 f/s, 7.5 - 30 m/s)

High velocity (>100 f/s, 30 m/s)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 largerFree-falling drops (gravity only)Cast offDrippingSplashingArterial spurting

22

Cast-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

23

Downswing of Hammer24

Cast-off from Weaponceiling25

Overhead swing with bloodied metal bar26

.Drip PatternFree-falling drops dripping into wet bloodLarge irregular central stainSmall round & oval satellite stains...37

Drip 1:Blood dripping into itself from height of 1 m (8 drops)38

Drip 2Blood dripping into itself from height of 1 m (8 drops)39

Dripping onto steps40

Splash PatternVolume > 1 ml Subjected to LV impact Thrown TippedLarge central irregular area surrounded by elongated peripheral spatter pattern41

Splash 1

5 ml blood squirted from a syringe from a height of 1 m42

Splash 2


Splash 3


Arterial Spurt PatternBlood exiting body under arterial pressureLarge stains with downward flow on vertical surfaceswave-form of pulsatile flow may be apparent50

Small arterial spurtspatterbroken pottery51

Neck incisions (scene)52

Neck incisions

Thyroid cartilageProbe in carotid arteryHesitation injuries53

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

54

Medium velocity blood spatter.Point of impact 15 cm in front of vertical target surface6 ruler55

High Velocity Blood Spatter

Blood 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 machinery58

Gunshot: back& forward spatterBloodstained foam held just above target surface.Back-spatter on entryForward spatteron exitBullet passing L to R just above sheet59

Gunshot Back SpatterArises from entrance woundPasses back towards weapon & shooterSeen only at close range of fireSeen on:inside of barrelexterior of weaponhand, arm, chest of shooter60

Back spatter on steadying hand61

Gunshot Forward Spatter Arises 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

62

Forward spatter (5 ms after bullet impacted at 1000 f/s)blood soaked targetbullet63

6 rulerForward spatter onto target placed 15 cm behind point of HV bullet impact (bullet passing towards screen) 164

Forward spatter (closer view)65

Forward spatter (closest view)5 mm66

Wipe PatternsObject moves through a wet bloodstainFeathered edge suggests direction

67

Transfer PatternsWet, bloodied object contacts a secondary surfaceTransfer from:hand, fingersshoes, weaponhairTransfer to:walls, ceilings clothing, beddingProduces mirror-image of bloodied object68

Transfer from hair (hair-swipe) 169

Transfer from hair (hair-swipe) 270

Flow PatternsBlood flows horizontally & verticallyAltered by contours, obstaclesOften ends in pool71

Flow pattern72

Trapped!73

Stabbing 174

Stabbing 275

Blood flow on shirtHorizontally to R side76

Pattern on shirt77

Bloodspots on trousers78

Fling Lab Pre-LabPurpose: To determine different characteristics of blood spatter patterns when using different weapons and different swing patterns.Setup: 8 groups total: 4 groups will be testing different swing patterns; 4 groups will be testing different weapon types.What needs to be done by tomorrow before the lab begins:Procedures written for how you are doing your test.Hypothesis about what you and your group expect to happen (and why).YOU NEED TO BRING GARBAGE BAGS THAT YOU CAN WEAR.

Blood Spatter Impact Angle Labhttp://www.nfstc.org/links/animations/images/blood%20spatters.swf

Blood Spatter Impact Angle Lab1. Measure the length and width of the splatter. 2. Divide the width of the splatter by its length. 3. Determine the arcsin of that number, typically using a calculator with an arcsin function.

Blood Spatter Impact Angle Lab1. Measure the length and width of the splatter. 2. Divide the width of the splatter by its length. 3. Determine the arcsin of that number, typically using a calculator with an arcsin function. (or p.523 in book)

Blood Spatter Impact Angle Lab1. Measure the length and width of the splatter. 2. Divide the width of the splatter by its length. 3. Determine the arcsin of that number, typically using a calculator with an arcsin function (or p.523 in book).

What impact angle did this blood drop hit?


w/l = 1.5/3 = 0.5


Arcsin(0.5) = 30

Blood Spatter Impact Angle LabPre-Lab: - Read through Lab 8-4 (p.229-233)- Draw the SETUP of one angle of your choice in your notebook. Note that each group will be doing ALL angles Find the angle of impact for the following blood drop dimensions:

#Length (cm)Width (cm)11121.164131.4141410.573556.2531.3

The following are slides that will help with labs for later on.

Angle of ImpactAdapted from Introduction to Forensic Sciences,W. Eckert, CRC, 1997

Gravitational dense zoneat lower edge14

Cast off Pattern (2/2) ? Sequence29

Cast off Pattern (2/2) ? Sequence1(4 spots)2(3 spots)3(2 spots)If weapon does not pick up more blood, spatter from subsequent backswings becomes progressively less.In practice weapon picks up more blood with each successful blow.

30

Three overhead swings with hatchet31

Cast-off & medium velocity spatter32

Cast-off & medium velocity spatter 233

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, machinery20

Cast-off Pattern? Object34

Cast-off Patternfrom Hand35

Cast-off pattern from bloodied hand swung in front of target6 ruler36

Splash onto vertical surface6 ruler10 ml blood thrown 1 m onto a vertical target surface45

Stamping in blood 1Area seen in close-up in next slide46

Stamping in blood Close-up of heel area47

A piece of pottery was broken on a person; the pottery pierced an artery, creating a few arterial gushes (the arc down), and eventually a pool of blood as the person stayed in the bed.**

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Blood Spatter & Crime Scenes