Bloodstain Pattern Analysis Can Assist In

•Bloodstain pattern analysis can assist in:

– corroborating statements,

–apprehending a suspect,

–reconstructing past events,

–exonerate the accused

•Properties of Human Blood

•Blood is a fluid which circulates throughout body and transports oxygen, electrolytes, nourishment, hormones, vitamins and antibodies to tissues and organs

•Composed of red blood cells (erythrocytes) and white blood cells (leukocytes), plasma and platelets

•Properties of Human Blood

•Blood is held together by strong cohesive molecular properties

•These properties create surface tension within each drop and on external surfaces

•Surface tension of blood is slightly less than that of water

•Blood does not fall in tear drop configuration

•Properties of Human Blood

•Volume of typical drop of blood = .05 ml, with an average diameter of 4.56 mm

•Blood is six times more viscous than water

•Specific gravity of blood is slightly higher than water

•These properties tend to allow blood to remain stable and resist alteration or disruption

•Properties of Human Blood

•Blood falling through air increases velocity until force of air resistance that opposes the drop equals downward gravitational pull – at that point, it reaches terminal velocity

•Estimate for maximum terminal velocity for free falling drop of blood was 25.1 ft per second (McDonell)

•Properties of Human Blood

•Diameter of bloodstain is due to:

–Function of volume of drop

–The surface texture it impacts

–Up to a point, the distance the blood falls.

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Target Surface Considerations

•Blood will not break apart unless an exterior force disrupts it

•Hard smooth surfaces (glass, smooth tile) create little spatter

•Wood or concrete create significant spatter

•Size, Shape and Directionality

•Geometry of bloodstains will generally allow for determination of their flight

•Narrow end of elongated bloodstain usually points in direction of travel

•After directionality has been determined, an area or point of convergence may be established by drawing straight lines through long axis of bloodstains

•Size, Shape and Directionality

•Points where lines converge represents the relative location of blood source in a two dimensional x and y axis

•This convergence location is an area, not an exact point

•Area of Origin – location of blood source, can also be determined three dimensionally

•Size, Shape and Directionality

•Impact angles are done by projecting their trajectories back to a common axis

•If angle of impact is 90 degrees, bloodstain is generally circular

•Impact angles of less than 90 degrees generally result in elliptical bloodstains

•Size, Shape and Directionality

•Width and length of elliptical bloodstain allows for calculation of angle of impact of original blood drop

•Width is divided by length to produce a ratio number

•Ratio is sine of impact angle: angle can be determined using a scientific calculator or sine function in trigonometric table

•Example of measurements

•Circular bloodstain: w =1.0, l =1.0 = ratio of 1, which corresponds to impact angle of 90 degrees

•Elliptical bloodstain: w = 1.0, l = 2.0 = ratio of .50, corresponds to impact angle of 30 degrees

•Spattered Blood

•Defined as a random distribution of bloodstains that vary in size and that may be produced by a variety of mechanisms

•Quantity of available blood can influence spatter

•Amount of force applied also influences spatter

•Spatter is created when sufficient force is available to overcome surface tension of blood

•Spattered Blood

•Spattered blood is significant because:

–Allows for determination of an area or location of the origin of blood source

–If found on suspect’s clothing, may place person at scene of violent altercation

–May allow the determination of the mechanism that created the pattern

•Classification of Blood Spatter

•LVIS - Low-velocity impact spatter – force of up to 5 ft/sec and stains are 4mm in diameter or greater

•MVIS – Medium-velocity impact spatter- force with velocity of 5-25 ft/sec. diameters of spatter 1- 3mm generally

•HVIS – High-Velocity Impact Spatter – force with velocity above 100ft/sec. diameters are predominantly smaller than 1 mm

•Classification of Blood Spatter

•Some analysts have discontinued prior terminology and focus on a more conservative approach:

–Identifying spatter created by an impact mechanism

–Identifying spatter created by a projection mechanism

•Spatters are dependent upon quantity of blood, force of impact and texture of surface impacted by blood

–Impact Spatter Associated with Gunshot

•Mistlike dispersions (less than .1 mm) are associated with spatter associated with gunshot

•May also be a wide size range from .1 mm up to several millimeters or more

•Size range is dependent on quantity of available blood, caliber of weapon, location and number of shots, and impeding factors, such as hair, clothes.

•Impact Spatter Associated with Gunshot

•Back spatter or blowback- associated with entrance wound and may be found on shooter or weapon, especially hand and arm area

•Forward spatter – associated with an exit wound

•Impact Spatter Associated with Beating and Stabbing

•Generally exhibits a size range from 1 to 3 mm

•Depends on force of impact and quantity of available blood

•First blow rarely produces spatter- Exposed blood must receive impact

•Type of weapon and number of blows have effects on patterns

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•Satellite or secondary spatter: single drops of blood producing small spatters around parent stain as a result of striking a rough target surface – circular and oval, .1 to 1 mm

•Drip patterns: multiple free-falling drops of blood produced from a stationary source onto a horizontal surface

•Dripped Blood

•Factors affecting this are:

– blood drop volume

– freshness of blood

– surface texture

–distance of vertical target from impact site

•Castoff Bloodstain Patterns

•Patterns are created by subsequent blows to the same general area where a wound has occurred and blood has accumulated

•Blood adheres to object producing injuries

•Centrifugal force generated by swinging of weapon is great enough to overcome adhesive force of blood, thus creating a castoff bloodstain pattern

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Splashed and Projected Blood

•Splashed bloodstain pattern- when quantity of blood in excess if 1.0 ml subjected to low velocity forces, or allowed to freely fall to surface.

•Secondary ricocheting may occur as a result of deflection

•Expirated Bloodstain patterns

•Expirated bloodstain patterns- blood which accumulates in lungs, sinuses and airway passages forcefully expelled

•May appear diluted if mixed with saliva or nasal secretions

•Air bubbles or vacuoles are not always present in this type of pattern

•Arterial Bloodstain Patterns

•Arterial bloodstain patterns are caused by breaching of artery and subsequent gushing or spurting.

•Pattern depends on:

–Severity of injury to artery

–Size and location of artery

–Whether injury is covered by clothing

–Position of victim at time of injury

–Usually large quantity of bloodstains

•Other Bloodstain Patterns

•Blood transfer pattern occurs when an object wet with blood comes into contact with an unstained object

•Altered bloodstains – are subject to change due to quantity of blood present, and temperature, humidity and air currents

•Other Bloodstain Patterns

•Skeletonized bloodstain - occurs when central area of a partially dried bloodstain is altered by contact or wiping motion

•Dried bloodstains age and go through color changes- red to reddish brown to black

•Clotting time assists in measuring amount of elapsed time since injury

•Other Bloodstain Patterns

•Clotted impact spatters may indicate additional activity, such as movement or further injury, occurred after initial bloodshed

•Evidence of coughing or exhaled blood may be associated with post injury survival time

•Bloodstains can be altered by wiping, smudging, wiping, or effects of moisture

•Other Bloodstain Patterns

•Suspected cleaned areas of bloodstains may be visualized with luminol

•Heat, fire or smoke may also alter bloodstain patterns

•Heat and fire can destroy bloodstain patterns

•Interpretations of Bloodstains on Clothing and Footwear

•Two questions arise with bloodstained garments:

–Whose blood is on garment?

–How was blood deposited on garment?

•DNA technology has assisted in identification of whose blood is present

•Interpretations of Bloodstains on Clothing and Footwear

•Two categories of bloodstain deposition onto garments

–Passive bloodstaining – transfer, flow patterns, saturation stains, and stains from dripping blood

–Active bloodstaining – impact spatter, arterial spurts, expirated bloodstains, and castoff.

•Interpretations of Bloodstains on Clothing and Footwear

•Bloodstain patterns must be identified and documented

•Serological findings should be reviewed before drawing conclusions

•Interpretation of bloodstain patterns centers on substantiating or refuting suspect’s version of events

•Interpretations of Bloodstains on Clothing and Footwear

•To facilitate examination of clothing by bloodstain analyst:

–Establish manner garments were collected, documented and preserved

–Document garments while victim or suspect is still wearing them

–Allow bloodstain pattern analyst to examine garments before removal for DNA analysis

•Interpretations of Bloodstains on Clothing and Footwear

•Take photomacrographs and photomicrographs of before cuttings or stains are removed

•Obtain a history of garment handling and where it has been – check for contamination or compromise of garment

•Documentation of Bloodstain Evidence

•Degree of significance of bloodstain pattern analysis can be enhanced by:

–Accurately documenting size, shape and distribution of the individual stains and patterns

–Including measuring devices within photographs

– Using more than one mechanism for documentation; photographs, video, diagrams, and notes

•Documentation of Bloodstain Evidence

–Collect articles of evidence that may contain significant or questionable bloodstain patterns, if possible

–Utilize overall, mid-range and close-up macrophotography when documenting bloodstain patterns – overlap photographs

–Documentation of Bloodstain Evidence

–Complete documentation in a manner which allows 3rd party to utilize the photographs, notes, diagrams, and video to place eh bloodstain patterns and articles of evidence back in their original location

–Remember, you can never take enough photographs

•The Use of Luminol Photography for Bloodstain Pattern Analysis

•Luminol is a chemiluminescent reagent that can be utilized both as a presumptive test for blood as well as a method of chemical enhancement of impressions in blood on various surfaces

•Used to check for latent prints or bloodstains where area has been cleaned by suspect or others

•The Use of Luminol Photography for Bloodstain Pattern Analysis

•Luminol is not specific for human blood- also reacts with animal blood

•Should be used in darker conditions

•Special photography should be used – 35 mm camera with a wide open aperture – f-2.8 or f-3.5 with an exposure time of 40 to 80 seconds

•Color film is preferred

•Photograph before and after application

•Absence of Evidence Is Not Evidence of Absence

•Absence of bloodstaining on an active participant can be explained by:

–Directionality of blows may direct spatters away from assailant

–Site of injury covered with clothing reduces spatter

–Assailant may clean up or change prior to being apprehended

–Assailant may have worn protective outerwear

•Absence of Evidence Is Not Evidence of Absence

–The assailant may have removed his clothing prior to assault

–Amount of blood present (bloodbath) may be due to active bleeding from victim who is still alive or draining of blood from wounds of a deceased victim

–Individuals have been known to confess to crimes they did not commit

•Report Writing

•Purpose of bloodstain pattern report is to convey findings of analyst to attorneys, court, and jury

•Report should include all overall observations and experiments from which final conclusions are rendered

•Report Writing

•Report should contain introduction, body and conclusions.

–Introduction - name of victim, suspects, case number, location of crime scene, list of materials and evidence, and who requested analysis

•Report Writing

–Body of report – crime scene description, physical evidence collected at scene, victim’s body and autopsy information, victim’s clothing and footwear, suspect’s body, suspect’s clothing and footwear, reconstruction, chemical enhancement techniques, experiments

•Report Writing

–Conclusion – findings should be listed in sequential order, limited to scientific foundations, fall within bloodstain analysis discipline, and expertise of analyst. Photographs and diagrams may accompany the report

•Training and Education

•There are a variety of experts from disciplines such as chemistry, biology, and physics

•It is highly recommended individuals enroll in a forty hour basic bloodstain interpretation course

•IABPA- International Association of Bloodstain Pattern Analysts, formed in 1983, is organization for this field of study.