CSI Ch. 11- Applying Bloodstain Pattern Analysis in Crime Scene

bloodstain pattern evidence is always a ____ characteristic

*class* -classification of a stain using its physical characteristics is a deductive conclusion, but recognition of its scene source is an inductive conclusion

major effort of BPA

*to identify the discrete patterns present in the scene and categorize each* -proper classification allows the analyst to eliminate many possible source events

blood dispersed in a jet (streaming ejection)

-leads to pattern of large stains that are often deposited either in linear patterns or in accumulations with associated spines and secondary spatter -blood volume escapes a point source flowing as a jet, breakup of jet leads to both stable droplets and large undulating masses of blood resulting in large spatter stains -stains across a surface --> linear pattern of relatively large volume spatter. jet directed in same area --> large accumulation -blood landing in accumulation --> spines and secondary spatter that radiate out from primary pattern -spatter stains deposited in liner form = spurts -large accumulations w/ irregular margins = gushes

fly spot patterns

-movement can track blood from body or blood source and deposit on surrounding walls and surfaces -also regurgitate blood on surfaces- mimic slightly impact spatter appearing as a number of small circular stains

voids

-not true patterns but a lack of staining in an otherwise continuous pattern -occur when a secondary object is present between a bloodstain event and a nearby surface -appear most often in spatter events -assist in understanding the relative position of items at the time of the event

non- linear spatter stain: impact patter: expectorate

-occur as a result of the breathing of the victim -blood present in the airway- exhalation breaks blood into small droplets -forced our of the airway

physically altered bloodstain principle

-once exposed, blood will react to environmental conditions (airflow, temp, humidity, variations of surface) in a predictable manner -simple recognition that blood dries, wicks, permeates and coagulates in and on surfaces in somewhat predictable fashion

linear spatter stain: drip trail

-pattern of individual spatter deposited on a surface , demonstrating movement of the dripping item from one point to another -criteria: in line distribution, consistent stain size range, stains lead from one point to another, stain size range 3-25 mm

phenolphthalein

-phenolpthalein, ethanol -h2o2 as an oxidizer -immediate pink color rxtn should occur in presence of blood

blood flows obey law of gravity

-presence of abnormal blood flows may indicate movement by the victim before death and/or disturbance of the scene

non- spatter stains

-primary stain is not a circular or elliptical shape, primary stain will not be a spatter -irregular margin: blood into blood, gush, smear: wipe, swipe -regular margin: pattern transfer, flow, pool, saturation

blood accumulates or flows on a surface

-produces patterns of accumulations with generally regular margins -"flows, pools, saturations"

amido black enhancement of blood

-protein stain that reacts to proteins present in blood -water based amino used only on static surfaces in scenes and not on evidence items -does not fix the blood and can interfere w/ subsequent analysis -effective for developing blood footwear marks on a variety of scene surfaces including floors and carpets -rxtn takes btwn 30 sec- 3 min -enhancement is blue-black in color

3 underlying principles that guide BPA

1. pattern diversity 2. stain shape and vector correlation 3. physically altered bloodstain (pab)

6 mechanisms of pattern diversity principle

1. static blood dispersed from a point source 2. dispersed in a jet (streaming ejection) 3. blood dispersed as function of accelerated motion 4. blood accumulates or flows on a surface 5. blood dispersed as a function of secondary. contact with a surface 6. blood dispersed as a function of gravity

2 primary field tests for presumptive presence of blood

phenolphthalein and leuco-malachite green

pattern diversity principle core concept

variations in combinations of blood volumes and forces acting on those volumes lead to recognizable classes of patterns

blood dispersed as function of accelerated motion

- forms linear pattern of spatter -force by movement overcomes adhesive force holding blood to object --> small jet of blood flowing off of the object or individual droplets that shear directly from object's surface -small droplets released from object, land across surrounding surfaces and deposited in linear orientations = "cast offs"

irregular margin non- spatter stain: gush/ splash

-a irregular pattern created when blood is ejected in volume -criteria: large volume accumulation evident in overall pattern, large irregular stain exhibiting spines and satellite spatter radiating form it, possible large elliptical stains around pattern -when a volume of blood is projected into the scene w/ minimal force or when a jet of blood is directed into same area -appear as large volume patterns w/ large elliptical stains surrounded by many secondary satellite stains -pressure behind ejection increases- number of secondary satellites and spines emanating from primary stains increase

irregular margin non- spatter stain: blood into blood

-a pattern of spatter deposited into one another or into another liquid, resulting in an accumulation w/ secondary spatter randomly oriented around the margin -criteria: pooling of blood or combo of blood and other liquid w. overlapping liquid, surrounded by random distribution of small satellite spatter w/ random variation in directional angles/ shapes -indicate blood source was relatively stationary at that point

presumptive tests for bloodstains

-based on oxidation- reduction rxtn of chemicals that occurs in the presence of heme, component of hemoglobin, primary o2 carrier found in rbcs -also reacts w other substance -a positive rxtn is not conclusive evidence for the presence of blood

methodology of bloodstain pattern analysis

-become familiar w/ entire scene -identifies discrete patterns among various bloodstained surfaces -classifies patterns based on their physical characteristics using some form of established taxonomy -evaluates aspects of directionality and motion in stain or pattern -evaluates angles of impact, points of convergence, areas of origin -evaluates interrelationships among stains, patterns and other evidence -evaluates viable source events to explain the patten -validates the analysis thru some form of peer review

blood dispersed as function of gravity

-blood drips from an object --> relatively consistent spatter -source may be replenishing or non replenishing -gravity draws the fluid downward where it collects on some aspect of object's surface -as volume of collecting fluid increases- its weight forces it away from that surface, resulting in a small column of fluid that connects the forming drop to the surface -weight of the mass overcomes surface tension of fluid, shears --> producing a large primary droplet and satellite droplets -dripping source is moving --> series of similar stains deposited on surface in random or linear patterns -dripping source is static --> accumulation - "drips, drip tails, blood into blood"

static blood dispersed from a point source

-blood mass is exposed to an external impulse or force --> radiating pattern of small circular and elliptical shaped stains -blood is incompressible and under force --> displacement -blood shears into small droplets and small spatter radiate outwards from source --> "impact patterns"

blood dispersed as a function of secondary contact with a surface

-blood may adhere to a nonabsorbent surface or be wicked into an absorbent surface -interaction leads to fluid being displaced on the original surface, transferred to a second surface or a combination of the two -"smears, wipes, swipes"

impact angle: as droplet collides with a target a right triangle is visualized

-by considering the diameter of the droplet, path of droplet, area on the target where the droplet first touches and terminates movement -major axis of blood stain= hypotenuse (bc) -minor axis of blood stain= side opposite (ab) -using trig sine and known measurements, solve for unknown angle (i) -circular shaped= < btwn 70-90 deg -bear claw shaped= < btwn 40-60 deg -long, elliptical= acute < btwn 30 deg or less

directional angle

-collapse of a free flight droplet on a surface produces a stain w/ a circular or elliptical shape -direction the droplets were traveling at the moment they struck a surface = directionality -based on collapse of the fluid droplet, the resulting long axis of the stain and scallops/ tails/ satellite stains around or on the stain -elliptical stains appear on side opposite initial contact point -spherical stains - scallops and tails appear in heavier concentration on side opposite initial contact point -reverse vectors defined by individual stain's directionality may converge in the scene

impact angle

-collapse of a free flight droplet on a surface produces a stain with a circular or elliptical shape -the ratio between the length of the long and short axes of the resulting stain has an empirical relationship to the angle at which the droplet struck the target -stable droplet strikes a surface creating a well- formed bloodstain, the resulting stain has a major and minor axis

directional angle + impact angle= corollary called area of origin

-considered together, the impact and directional angles for a number of stains associated w an impact event may define the origin of the stains in 3 dimensions -vectors define by angles will usually converge in 3d space -area where stain vectors converge provides indications of where the corresponding droplets originated their flight

documenting bloodstain patterns

-each pattern must be documented w/ overall photos of that pattern alone as well as detailed close up photos of pattern or selected individual stains within the pattern -*close up detail is a critical factor in bloodstain pattern photography* -road mapping is the most effective way to document bloodstained scenes -sampling of each pattern ensures that the pattern can be identified back to a specific source

non-linear spatter stain: impact pattern

-radiating pattern of small circular or elliptical shaped stains created when blood is broken up as a source by some force -criteria: series of related small spatter stains, deposited in a pattern that has a radiating distribution, progressive change in individual stain shape further out in the pattern, various sizes range of parent stains but generally consistent -spatter radiates from a central location -occurs primarily where a blood source is compressed nay an impact of some nature

luminol enhancement of blood

-reacts in presence of heme by producing a chemiluminescence that has a blue/ green coloration -as an odixation rxtn, luminal reacts to a number of items and products found in household -false positives differ in color, duration, intensity -positive rxtn will initiate in a matter of several seconds after application and remain active for several minutes -slr w/ extended shutter duration up to 3-5 min -mounted on tripod, shutter help open w/ lock down shutter release calle

fluorescein enhancement of blood

-reacts to heme in blood -response is observed only under an als -solution will fluoresce green when viewed w/ all at 455-485nm with yellow* barrier filter (or orange) -solution: dh2o, Noah, fluorescein and zinc -finer the spray produces, the more effective the rxtn

non- linear spatter stain: drips

-spatter resulting from blood dripping from an individual or otherwise bloodied object -criteria: one or more spatter stains, parent stains have generally large diameter (3-25 mm), randomly oriented on a surface

droplet of liquid in flight has this shape

-spheroid -any measurement of diameter of the droplet will be equal

regular margin non- spatter stain: pattern transfer

-stain or pattern created by the transfer of blood from one object to another in which a recognizable characteristic or image is present in the pattern -criteria: contact patter, angular demarcations, curves or other recognizable characteristics or an image of the source object, deposited in a series

irregular margin non- spatter stain: smear

-stain/ pattern created by transfer of blood from one object onto another, thru some form of contact -criteria: irregular shape stain, continuous or feathered boundary, striations in body of stain, diminished volume of blood across the body of the stain, evident displacement of blood -wipe= smear thru a preexisting stain or pattern -swipe= smear where blood is deposited onto the surface

principle of stain shape and vector correlation

-the shape of certain bloodstain provides indications as to the direction of deposition as well as to the spatial organ of the blood -includes: directional angle and angle of impact

spatter stains

-when a blood mass is broken up into small droplets and put into free flight by some mechanism --> strike a surface and produce circular or elliptical shaped stains -linear: spurt, cast off, drip trail -non-linear: impact, expectorate, drip

linear spatter stain: spurt

-when blood is ejected in a stream under pressure or with velocity; most often encountered when an artery or heart is breached -criteria: series of related spatter stains, large volume in individual stains, lines of stains or overlapping stains deposited in: V's, arcs, serpentine pattern, large elliptical stains

linear spatter stain: cast- off

-when blood is fluid from an object that is either in motion or which suddenly stops some motion -criteria: series of related spatter stains, deposited in a linear or curvilinear orientation, consistent parallel directional angles in stains to overall pattern, consistent change in impact angle in pattern

infrared photography

-with the majority of the visible light eliminated, the fabric appears white, while the blood. with its high absorbance appears black

leuco-malachite green

-yields a green color rxtn

a final consideration in bloodstain pattern documentation

accurately place the pattern in the scene

saturation stains occur when

blood is drawn into clothing, cloth or permeable surfaces