2 What is a Bloodstain Pattern? A bloodstain pattern is a physical, geometric image created by blood contacting a surface, or by a surface contacting blood.The images of interest are primarily those created once blood leaves the body.
3 Bloodstain Pattern Analysis Bloodstain pattern analysis is the interpretation of information presented by bloodstain patterns.It involves pattern recognition and interpretation of the blood.Bloodstain evidence at a scene can be very useful in helping to reconstruct actions that took place at a scene, corroborating witness statements, and identifying suspects. The evidence is physical evidence. All information offered as originating with bloodstain interpretation must be supported with careful documentation and accurate analysis.
4 Physical Evidence Bloodstain patterns are physical evidence. All information offered as originating with bloodstain interpretation must be supported with careful documentation and accurate analysis.
5 Analysis of Bloodstain Patterns Analysis involves an understanding of the physical properties of blood: surface tension, viscosity, drop formation, specific gravity, in flight behavior.
6 Probable Information From Bloodstains DirectionAngle of ImpactOriginApplicable ForcesTrajectories of ForcesObject IdentificationNumber of Blood Initiating or Altering EventsVictim/Perpetrator PositionsSequence of EventsLeft Handed/Right HandedClothed/Unclothed“Psychoscene” Presentation
7 Physical Properties Affecting Bloodstain Patterns. What item caused the blood stainWhat surface did it land on?TemperatureHumidityCapillary ActionTimeHow well the blood sticks to the surfaceVictim MovementContamination of crime sceneDistanceOrigination Initial ForceVolumeSurface Tension (Bevel and Gardner, 2002).
8 Impact Surface Considerations Course surfaces cause irregularities in patterns.Blood may break up on impact, and may follow the contour of a surface.Impact angles and directionality become less reliable as a surface become more porous.
9 Some General Characteristics of Moving Blood Age, sex, race, nor alcohol blood levels seem to affect the patterns producedTerminal velocity is generally reached 6’-8’.Larger drops tend to project further than smaller drops.After about 6’, increased distance fallen does not affect stain size.
11 Passive Patterns Passive Flow Pattern – when blood flows freely. Passive Saturation Pattern –when blood flows to saturate an area.
12 Passive Patterns (Cont.) Passive Saturation – in cloth there may be secondary patterns from the cloth folded on itself. Passive Pool Pattern – when blood flows freely into a pool.Notice: trail, drip.traildrip
13 Passive Patterns (cont.) Free flow around a surfacenotice pattern from lap and buttocks.Notice void areas in thispassive pattern.
14 Projected PatternsPatterns resulting from blood sent with a degree of energy to a surface. Blood is shot, flung, or hurled at a surface, as examples.Arterial Spurt/Gush Pattern- blood which leaves the body under pressure: breached artery.Arterial Spurt and Free Flow
15 Projected Patterns (cont.) Expirated Pattern – blood projected from the mouth, nose, or a gaping wound. The victim had a throat wound.
16 Projected Patterns (cont.) Expirated patterns have the appearance of medium to low velocity blood spatter.Expirated patterns may also be found with arterial spurt patterns, and cast-off patterns.Expirated Pattern with Arterial Spurt.
17 Projected Patterns (cont.) Instrumental Projected Patterns – Patterns are caused, in part, by an instrument.Examples of instruments are:knife, firearm, board, swinging hand, kicking foot, bat.The blood is projected from the instrument.High Energy - Shotgun
18 Projected Patterns (cont.) Instrumental Projected Patterns:-High Energy (velocity): 100’/sec or more, firearms, airplane propeller, power equipment.-Often has a misting effect appearance, and spatters less than 1mm in diameter.-In the photos note the mass and misting areas.suicidetest pattern
19 Projected Patterns (cont.) Instrumental Projected Patterns:-Medium velocity: 25’/sec or more, swinging knife, bat, kicking foot, swinging hand, expirated, arterial.-No predominance of stains with a diameter less than 1mm.-A trail may present in a pattern from a swinging instrument (+1 rule).Medium energy(velocity) with transfer pattern.
20 Projected Patterns (cont.) Instrumental Projected Patterns:Low Velocity: free falling velocity, blood dropping from a cut finger, bleeding nose, other wounds, or a near immobile instrument.Bleedings, walking subjects may leave a low velocity trail.drops at homicidedropped blood
21 Projected Blood (cont.) Size difference in free falling drips can be due to: distance, surface from which blood is dripping.Blood dripping into blood: notice the smaller “satellite” stains -satellite
22 Projected Blood (cont.) Instrumental Projected Patterns:-Cast off: a special term reserved for spatters cast from an instrument.-cast off patterns seem to particularly apply to sharp force and blunt trauma instruments.cast off from fleeing suspect
23 Projected Patterns (cont.) Instrumental Projected Patterns:Cast off: A moving instrument may produce a pattern in which the blood spatter creates a “trail”. The “trail may reproduce several times. A very general rule is that the number of blows to a victim is one more than the number of “trails”. *caution*.Cast off “trail” on back side of pajama bottom –notice multiple “trail” or “arc” phenomena.
24 Projected Patterns (Cont.) Projected blood forming an arc that was from an assault with a hammer.Notice the mixture of patterns.arc
25 Projected Patterns (cont.) Additional arc patterns, consistent with being struck with an object, are evident in the photo.Notice the mix with the contact pattern.The victim reported being repeatedly struck while covering up and trying to get away.Are the patterns consistent with the story?arccontact
26 Projected Patterns (cont.) Instrumental Projected Patterns:Backspatter: generally applies to firearm phenomena in which the blood from the wound is also forced backwards onto the subject of a surface.-hands are common backspatter surfaces.-very easy to confuse with expirated blood.backspatter from gunshot wound.
27 Summary of Impact Patterns Impact patterns: produced when blood splashes.May be produced from blood falling into blood, or an object impacting blood.These patterns are called splash patterns in some literature.Characteristics: “spiny” edges, circumferential surrounding stains.Volume pattern: a volume of blood impacts surface, and falls into itself. Notice the radiating patterns.
28 Impact Patterns (cont.) Drip: when blood drips into blood.Object splash: when an object impacts a volume of blood.
29 Impact Patterns (cont.) Blood drips into blood and splashes onto the chair leg.An assault victim leaves a blood trail - notice the dripping, splashing, and adjacent bloodstains.
30 Impression Patterns Transfer: notice outline of Patterns created: surface contacts a surface leaving an impression.transfer: bloody surface to secondary surface (bloody hand to wall).contact: object surface contacts blood (shoe print)swipe: bloody object moves across surface(hair).wipe: object moves through blood (hand through drop).Transfer: notice outline ofof parallel liner line pattern.This is a pattern from a armtouching the table.
31 Impression Patterns (cont.) Notice the swipe patterns onthe wall, and by the foot.Notice the wipe through theblood with the feathering ofthe stain, and the swipe tothe left.
32 Impression Pattern (cont.) Wipe: Notice the remaining skeleton of the original stain. The “feathering” out of the swipe indicates direction.Wipe: A little more difficult to tell. It almost looks like a swipe. This was made with a brush.
33 Impression Patterns (cont.) A transfer pattern from theshotgun to the bed sheet.Knife blade and handle transfers.
34 Impression Patterns (cont.) A contact pattern from a shoe at the scene of an assault.Knife transfer patternfrom a homicide scene.Notice the handle pattern in the far left.
36 Impression Patterns (cont.) A transfer swipe pattern fromThe scene of an assault.notice the mixture of thetransfer, free flow, and castoff patterns.A very subtle swipe markin carpet at the scene of ahomicide. The marks start at upper center and arc downward.
37 Impression Patterns (cont.) Impression patterns may be enhanced by the use of bloodstain dyes (Amido Black, Coomassie Blue), Luminol, Alternate Light Source, or Fluorescein.Since identity can often be established by DNA, a sample of any pattern should be taken prior to enhancement.Would Luminol have aided the carpet pattern in the previous slide?Luminol enhancement
38 Blood On Clothing Directionality determinations are possible. Contact, transfer, & passive actions usually on one side.Projected related actions, volume actions usually on both sides.**The most difficult of all interpretations?**
39 OriginOrigin refers to the place from which the blood came in space. It is a physical location.For multiple stains the origin can be determined in a two dimensional aspect by drawing lines through the center of the stains in the direction of travel and in the corresponding reverse direction, and observing the point (area) of convergence.**The origin corresponds to the opposite direction of the direction of travel.**Lines drawn through bloodstain patterns to determine convergence.
40 Origin (cont.)A three dimensional point of origin can be determined by several methods.- stringing: placing strings along the direction of travel and the angle line of the angle of impact.-computer models.-mathematical: using right angle triangle procedures.Mathematical charting in preparation for determining three dimensional origin. If one angel and one side are known, the others can be determined.
41 Visual Indications of Origin Some analysts prefer to use strings to visualize origin.A quick generalization of probable origin is to sue colored markers that are aligned on the axis of the direction of travel.
42 DocumentationPhoto show direction of travel is approximately 59 degrees. (or 239).Arrow and notation indicate zero to right and north.Arrow through center points to direction of wipe.
43 Blood For Purposes of Reconstruction Identity Locates Victims/PerpetratorBloodstain Patterns Locate ActionsVictim/Perp + Actions Suggest ScenarioScenario May Suggest MotiveMotive May Suggest The CrimeSolution Depends Upon Proof: Victim/Perp, Actions, Evidence, Scenario, Motive, and Crime.
44 Blood As Evidence Chain of Custody is essential. Photograph- if applicable.Measure – if applicable.Contamination controlUse clean instruments or clean instruments..Document patternsDry blood is best.Chain of Custody is essential.Describe appearance.
45 Identifying and Enhancing Blood Physicality – does it look like blood, smell like blood, act like blood, and should it be blood.Positive identification is only by laboratory analysis.*False positives are possible with all tests and enhancements.*Luminol – strong reaction, short term, carcinogenic.Fluorescein – strong reaction, very sensitive, can be used in daylight, requires ALS.Amido Black – heavy staining, carcinogenic.LeucoCrystal Violet – easy to mix, strong staining, carcinogenic.Hungarian Red – requires ALS, white lifters.Coomassie Blue – good stain, easy to use.
46 Bloodstain Pattern Analysis: Summary and Conclusion Bloodstain pattern analysis is a scientific application with limitations.One cannot make assumptions beyond the best possible explanation.Bloodstain pattern analysis is a component part of the total investigation.