Bloodstain Pattern Evidencw Flashcards
What is bloodstain Pattern Analysis?
Feature-based pattern recognition that studies the shape, size, location and distribution of bloodstains.
What type of information is provided by bloodstain pattern analysis?
Provides information about the event(s) that created the bloodstains and patterns
What is meant by BPA being an applied science?
A science based upon severak other scientific disciplines.
List the other disciplines BPA is based on.
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Biochemistry
Physics
Fluid mechanics
Trajectory analysis
Chemistry
In what types of investigations is BPA used?
5
Homicides
Non-homicide death investigations
Serious assaults
SAs
Serious industrial accidents
What information can BPA provide?
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Impact location(s)
Minimum number of impacts
Object or mechanism used to create pattern
Position of person bleeding
Movement of people and objects during bloodshed
Movement of people and objects after bloodshed
Sequence of events
Describe the contributions Dr. Edouard Piotrowski made to BPA.
3
Recognized the dynamic nature of blood in flight asa result of blows
Conducted experiments striking live rabbits with various implements
Documented the resulting bloodstain patterns through hand drawings.
What was the significance of The Queen vs. Campbell 1872?
Dr. Moore Sr. and Dr. Foster describe bloodstains found on the suspect’s dress found on scene
What was the significance of R. vs. McPherson & Burke 1878?
Professor Ellis described bloodstain found on the suspect’s clothing.
Stated that the trousers had been washed after being bloodstained, based on chemical tests for blood.
When did Dr. Fred Carter develop software for blood drop simulation and area of origin calculations?
1989
Outline the process of becoming a bloodstain pattern analyst in Canada.
5
Understudy program ~2-3 years
Classroom study
Lab experiments
Scene attendance with mentor
Written and practical assessments
About how many bloodstain pattern analysts are there in Canada?
20-30
When was the International Association of Bloodstain Pattern Analysts formed?
1983
What was the purpose of the International Association of Bloodstain Pattern Analysts?
Professional org established to exchange ideas and standardize BPA practices.
How much blood is in the average adult?
~5 L
Describe the composition of blood.
55% plasma
45% erythrocytes
<1% leukocytes and platelets
What type of fluid is blood?
Non-Newtonian
What is viscosity?
Resistance to movement or flow
Compare the viscosities of blood and water.
Blood is approx. 3-5 times more viscous than water
Describe surface tension of blood.
Elastic like property of the surface of blood that tends to make it contract.
Describe what surface tension is.
A molecule in a liquid is attracted to surrounding molecules.
A surface molecule does not have molecules above, attraction is not balanced.
This creates a net force towards the inside of the liquid, pulling the surface molecule inward.
Describe what is meant by blood being a non-Newtonian fluid.
Blood viscosity decreases as shear force is applied.
Why is the non-Newtonian fluid property of blood important?
It allows blood to move through small blood vessels.
Give examples of other shear-thinning fluids.
Ketchup
Whipped cream
Motor oil
Give examples of shear-thickening fluids.
Oobleck
Silly Putty
Honey
True or false: The ability of blood to form specific patterns affected by things such as age, sex, alcohol/drugs and disease.
False, none of these factors have any significant affect on the ability of blood to form specific patterns.
Why are we able to rely on assessment of bloodstain patterns?
The patterns that blood produces are predictable and reproducible.
What are the three primary classificaitons of bloodstain patterns?
Gravity
Transfer
Spatter
What is an altered stain?
A bloodstain with characteristics that indicate a physical change has occurred.
Give examples of altered stains
Dilution
Insect activity
Drying
Clotting
Serum separation
Decomposition
What is void?
An absence of blood in an otherwise continuous bloodstain or bloodstain pattern.
What are gravity/passive bloodstain patterns?
Bloodstains/patterns created or formed by the force of gravity alone.
List the types of gravity patterns.
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Drip stain
Drip trail
Drip pattern
Splash pattern
Pool
Saturation stain
Flow
What is a drip stain?
A bloodstain resulting from a falling drop that formed due to gravity.
What does the formation and appearance of bloodstain patterns depend on?
Surface
What is an accompanying drop?
A small blood drop produced as a by-product of drop formation.
What is a drip trail?
A bloodstain pattern resulting from the movement of a source of drip stains between two points
What are some characterisitcs of a drip trail?
Scalloped edge with satellite spatter
What is a drip pattern?
A bloodstain pattern resulting from a liquid that dripped into another liquid, at least one of which was blood.
What is a splash pattern?
A bloodstain pattern created from a large volume of blood falling onto a surface.
What is a pool pattern?
A bloodstain resulting from an accumulation of liquid blood on a surface?
What is a flow pattern?
A bloodstain resulting from the movement of a volume of blood on a surface due to gravity or movement of the target.
What is a saturation stain?
A bloodstain resulting from the accumulation of liquid blood in an absorbent material.
What is a transfer bloodstain pattern?
A bloodstain resulting from contact between a blood-bearing surface and another surface.
List the different types of transfer patterns.
3
Transfer pattern
Swipe pattern
Wipe pattern
What is a swipe pattern?
A bloodstain resulting from the transfer of blood from a blood-bearing surface onto another surface, with characteristics that indicate relative motion between the two surfaces.
What is a wipe pattern?
An altered stain resulting from an object moving through a preexisting wet bloodstain.
What is a spatter bloodstain pattern?
A bloodstain resulting from an airborne blood drop created whenexternal force is applied to liquid blood.
List the different types of spatter patterns.
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Projected pattern
Cast-off pattern
Cessation pattern
Expiration pattern
Impact pattern
Firearms related spatter
Describe the relationship between stain size and energy applied.
More energy applied = smaller stain
Describe the relaitonship between distance travelled and stain size.
Further distance travelled = smaller stain
What is a projected pattern?
A bloodstain pattern resulting from the ejection of blood under hydraulic pressure, typically from a breach in the circulatory system.
What is a cast-off pattern?
A bloodstain pattern resulting from blood drops released from an object due to its motion.
What is a cessation pattern?
A bloodstain resulting from blood drops released from an object due to its abrupt deceleration.
What is an expiration pattern?
A bloodstain pattern resulting from blood forced by airflow out of the nose, mouth or wound.
What is a bloodstain pattern from firearms?
An impact pattern created through the transfer of kinetic energy from a projectile to the body.
What is a forward spatter pattern from firearms?
A bloodstain pattern resulting from blood drops which can be produced when a projectile creates an exit wound.
What is a back spatter from firearms?
A bloodstain pattern resulting from blood drops which can be produced when a projectile creates an entrance wound.
What can impeded forward and back spatter?
Intermediate barriers like clothing
What is an impact pattern?
A bloodstain resulting from an object striking liquid blood.
What is meant by bloodstain directionality?
The characteristic of a bloodstain that indicates the direction blood was moving at the time of deposition.
What is the angle of impact?
The angle, relative to the plane of a target, at which a blood drop strikes the target.
What is the area of convergence?
The space in two dimensions to which the directionalities of spatter stains can be retraced to determine the location of the spatter producing event.
What is the area of origin?
The space in three dimensions to which the trajectories of spatter can be utilized to determine the location of the spatter producing event.
Outline the scene approach of a BPA.
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Document scene
Minimize and document scene changes
Search for blood
Enhance latent blood pattern
Identify patterns
Sample collection
Area of origin analysis
Formulate and test hypotheses
Report findings
What characteristics of bloodstains do BPAs make note of?
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Shape
Size
Location
Distribution
Does the tail of a drip trail always indicate the direction a person was walking?
No
What is a characteristic of a splash pattern?
More spinous and can travel pretty far
What is potential type of information that could be gleaned from a flow pattern?
Movement
Describe the characteristics of a transfer pattern.
Uneven distribution of blood throughout the stain.
Describe some characteristics of a swipe pattern.
Striations, feathering, snow plow effect/welling
Describe the characteristics of a projected pattern.
Spines
Waves
Drops
Arc
Describe the characteristicss of a cast-off pattern,
Blood goes off at a tangent
Linear arrangement
Give examples of situations that may cause a cessation pattern.
Door knobs (most common)
Light switches
Describe characteristics of an expiration pattern
Dilution
Air bubbles
Mucous strands
Range of sizes
